DECEMBER 2002 - Volume I - Issue 1

php|architect The Magazine For PHP Professionals

Zeev Suraski - Brad Young PERFORMANCE MANAGEMENT OPPORTUNITIES

This copy is registered to: Liwei Cui [email protected]

Comparing PHP With the Industry at Large

Reviewed for you: Zend Performance Suite Davor's PHP Editor

Plus:

SNMP Management With PHP PHP nCurses Shell Programming Writing a Webmail System Distill PDFs For Free With PHP Create a DB Abstraction Layer

SUBSCRIBE AND

WIN!

In Colaboration with

The designers of PHP offer you the full spectrum of PHP solutions

Serve More. With Less. Zend Performance Suite Reliable Performance Management for PHP

Visit www.zend.com for evaluation version and ROI calculator

Technologies Ltd.

TABLE OF CONTENTS

php|architect Departments 4

| Editorial rants

Features 9

|

Performance Management Opportunities

INDEX

by Zeev Suraski and Brad Young

5

| New Stuff

14

|

Curses! Writing Cool Shell Applications With PHP

6

by Marco Tabini

| PHP-Win A Look at Davor’s

25

|

PHP Editor

SNMP Management With PHP by Harrie Hazewinkel

61

| Product Review Zend Performance Suite

34

|

Database Abstraction Layers

Version 2.5

65

| Tips & Tricks

A Concrete Look at by Maxim Maletsky

41

|

Creating A Visual Catalogue System with PHP and IE

by John W. Holmes

by Davor Pleskina

70

| For Your Reading

49

|

Writing a Web-based

Pleasure

PDF Converter

Book Reviews by the

by Marco Tabini

php|a team

72

| Exit(0); A War With No Enemies

December 2002 · PHP Architect · www.phparch.com

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|

Directing Mail with qmail’s Maildirs by Jonathan Sharp

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EDITORIAL RANTS

EDITORIAL

H

ere we are. After months of preparations—and a few sleepless nights—you hold in your hands the very first copy of php|architect! While most editors will spend their first editorial explaining at length the arduous path the brought the fruit of their labor to life, I feel I have a higher goal to aspire to. Getting php|a off the ground has introduced us to some genuinely new experiences—nothing beats being awake at two o’clock in the morning (when you couldn’t read the lettering off a truck if it hit you) trying to pick a highly legible font that will work both on the screen and in print. Still, I don’t think you want to hear about that. Let me, instead, give you an idea of how this issue is organized, so that you can take advantage of it to its fullest potential. We chose PDF and electronic distribution as a move that, we thought, would drive down our costs and, in turn, make it affordable for anybody in the world to subscribe or buy a single issue of php|a. Still, we recognize that there are some unique challenges related to using this distribution strategy, and we have taken a few steps that (we hope) will make it easier for everyone to enjoy our magazine. The PDF file that you have received has been designed both for on-screen viewing and for printing on a regular inkjet or laser printer. This way, you can look the contents over directly on your computer, and you can print whatever interests you—or the whole thing, if you like the feel of paper in your hands. In fact, although the PDF file itself

is encrypted and you should not redistribute it electronically, you can print as many copies of it as you like. If you decide that on-screen viewing is your bag, then here are a couple of pointers. Most of our articles are hot-linked to the Internet—whether it’s an e-mail address to contact an author or the URL of a website from which you can download some great information. Links are an opportunity for us to offer you something that a print magazine will never be able to—a direct connection to the world. Naturally, all our advertisements are also linked—so, show us your support and do visit our advertisers’ websites. They all offer great products. No, really, they do! To make the navigation easier, you will find a full table of contents, which can be accessed from within Acrobat’s bookmarks tab. Notwithstanding all these steps we’ve undertaken, PDF remains a “new” way of publishing a magazine, and we can only hope to get better with time. Your feedback in this process is crucial—we want to hear what we’ve done right, but, especially, we want to hear what we’ve done wrong, so that we can fix it. Drop us an e-mail at [email protected] and let us know what you like and don’t like, what topics you want to see discussed in future issues and any comments you may have about this month’s articles. Happy reading!

December 2002 · PHP Architect · www.phparch.com

php|architect Volume I - Issue 1 December, 2002 Publisher Marco Tabini

Editors Arbi Arzoumani Marco Tabini

Graphics & Layout Arbi Arzoumani

Administration Emanuela Corso

Authors Arbi Arzoumani, Harrie Hazelwinkel, John W. Holmes, Maxim Maletsky, Davor Pleskina, Jonathan Sharp, Zeev Suraski, Marco Tabini, Brad Young

php|architect (ISSN 1705-1142) is published twelve times a year by Marco Tabini & Associates, Inc., P.O. Box. 3342, Markham, ON L3R 6G6, Canada. Although all possible care has been placed in assuring the accuracy of the contents of this magazine, including all associated source code, listings and figures, the publisher assumes no responsibilities with regards of use of the information contained herein or in all associated material.

Contact Information: General mailbox: Editorial: Subscriptions: Sales & advertising: Technical support:

[email protected] [email protected] [email protected] [email protected] [email protected]

Copyright © 2002 Marco Tabini & Associates, Inc. — All Rights Reserved

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NEW STUFF

NEW STUFF

Open-source Gets a Rap-around As open-source software becomes more and more accepted as a viable alternative to its commercial counterpart in IT industry, it’s becoming painfully obvious that it’s necessary to build an infrastructure to facilitate the exchange of information between developers and customers. Thanks to its open nature, OSS lends itself well to customization— something that is normally unthinkable with commercial products. Since there is no licensing cost, companies find it easy to use opensource projects as the basis for larger initiatives that have very specific requirements. This results in ad-hoc solutions that are based on solid, well-tested code and can be deployed in a short time. Open-source developers are in the unique position of possessing the knowledge needed to successfully market customization and special features to their software

You’ve got a great software product and committed users, but you need additional funding to develop the features they require. packages. Unfortunately, they often suffer from a lack of exposure that would allow them to defray development costs of new features by offering such features to multiple customers at the same time. Marcheka Software Ltd. aims at filling the void between OSS vendors and clients through their Rap-X offering, which can be found at http://www.rap-x.com. Labeled as a “collaborative sales & support platform”, Rap-X works by allowing prospective clients to make requests for new features to be added to software packages in a collaborative way, so that multiple requests for similar changes can be merged into a single one and the development costs can be amortized among several players. With this approach, everyone ends up a winner: developers get the exposure they need and can open

December 2002 · PHP Architect · www.phparch.com

new markets for their products while still benefiting the public at large by keeping their products free. Customers, on the other hand, benefit from the fact that they can enjoy customized software at a fraction of the costs normally associated with it. Rap-x, which already counts five different opensource projects among its clients, is offered both as an ASP (as in Application Solutions Provider, not Active Server Pages!) product and through a more traditional licensing model. You can find its website here. PHP 4.3 Inches Nearer With the release of RC 2 at the end of November , the new PHP version 4.3 is one step from its final release. The new version of our beloved language includes several enhancements and performance optimizations compared to its predecessor. Our favorite one is the ability to fetch SSL-protected pages directly through the fopen() URL wrappers—a major step forward, in our opinion, toward making PHP ever more appealing for commercial applications. You can download PHP 4.3 RC2 from the PHP Group’s main page. Sessions, Anyone? Farpointer Technologies has released a new session management tool for Apache called iConductor. Yes, we know, PHP already supports session management. iConductor, however, is interesting because it does so independently of PHP (or any other language) by hooking directly into Apache. This makes it possible, for example, to manage sessions directly from within HTML pages, which, in turn, could mean lower overhead when processing pages. iConductor costs $1,295.00 and is available directly from Farpointer at http://www.i-conductor.com.

php|a

5

PHP-WIN

PHP-W WIN

Reviewed For You

Davor’s PHP Editor By Arbi Arzoumani

F

or a vim addict (recently converted to using gvim and the open-source CREAM extension) like myself, GUI IDEs are something to look at with an air of suspicious resentment. On one hand, they often look easy to use and user-friendly (something that can’t really be said about vim). On the other, however, my shell junkie friends and I fear that, as soon as you need to do something out of the ordinary, they will turn into rigid monsters that won’t allow you to move past their pre-set functionality. Luckily, I’ve had a chance to find out that it’s not necessarily always the case. After having been scarred for years by Microsoft’s Visual Studio IDE, I had a chance to use Zend Studio, which I found extremely powerful (particularly in its debug functionality, which are very valuable), although made a little slow by the fact that it’s based on Java. Still, even for its price, Zend Studio is extremely good—and works across multiple platforms. A few weeks ago, I came across Davor Pleskina’s PHP Editor (DPHPE from now on), which is available from his website at http://www.pleskina.com. Davor is a great guy (he’s also the author of this month’s article on catalogue management), and he suggested that I give his IDE a try. Firing Up DPHPE is extremely easy to install, although it doesn’t come with a setup program of its own. You do have

December 2002 · PHP Architect · www.phparch.com

to manually copy the files from the ZIP file you can find at Davor’s website into a folder on your PC and create the necessary shortcuts. I can’t see this as being a huge problem, since it’s safe to assume that you probably have some level of confidence with the OS if you’re interested in this product. Still, creating a setup program is not a particularly challenging endeavor these days—there are plenty of tools for that—and a more guided approach to installation would probably benefit most users. To give you an example, during my first attempt at running DPHPE, I simply executed the application’s main executable from directly within WinRAR (my compression application) without copying any supporting files. The results were not catastrophic—the application was running fine for the most part—but I had lost access to some functionality, such as keyword autocompletion.

DPHPE is also able to maintain a list of all the variables that are currently in scope in your script... Once installed, DPHPE takes up very little space on

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Davor’s PHP Editor

your hard drive, which luckily also means that it uses very little RAM when it has to run. As much as this doesn’t seem to be a big problem these days, if your machine is running a number of different services at the same time, the last thing you need is another application that gobbles memory.

Another well-developed feature of DPHPE is the ability to create and maintain projects. Basic Features Where do I begin? DPHPE has a wide array of different features that are undoubtedly helpful for any developer. Most impressive of all, these features are implemented in a simple and efficient way, so that they actually help without getting in the way (at least most of the time). The editor that comes with the application features syntax highlighting (for HTML, PHP, Javascript and CSS), and its aspect is fully customizable—both

December 2002 · PHP Architect · www.phparch.com

from the point of view of the fonts used and of the colours in which the syntax is rendered. Also featured in the editor is the ability for auto-completion of keywords, which is particularly useful for a language as complex as PHP. It is also possible to have the application create a list of functions defined in your scripts, although this doesn’t always work well—for example, I had a comment that contained the word “function”, and the editor mistakenly recognized it as a declaration. DPHPE is also able to maintain a list of all the variables that are currently in scope in your script (although, unfortunately, it is unable to extend this capability to any include files you may be using) and to automatically pop up a window that allows you to choose a variable whenever you type the dollar sign. This feature tends to be a bit annoying after a while, but it can be turned off and the variable list can be used manually as needed. My only real beef with the editor is that I couldn’t find a way to word-wrap my long lines of code. Not everyone uses this feature, but I find it very convenient and not having it makes it a bit difficult to use the editor in a comfortable way.

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PHP-WIN Project Management and Web Preview Another well-developed feature of DPHPE is the ability to create and maintain projects. A project is simply a repository of files but, contrary to a folder, it also possesses a number of properties that make it possible, for example, to preview entire web projects at the click of a mouse. What’s most interesting, however, is that the concept of projects lays the foundation for a number of future expansions, such as encoding, CVS or SourceSafe compatibility, global search and replace, and so on, that could all be accessible at the click of a mouse. Speaking of web preview, if you have Internet Explorer installed on your machine (which you must have, unless you’re running some ancient version of Windows), DPHPE is capable of interfacing to it and visualizing your PHP scripts by executing them through your web server. If you prefer, you can also launch IE separately rather than within the editor. Unfortunately, DPHPE does not feature an internal debugger—and I personally think

December 2002 · PHP Architect · www.phparch.com

Davor’s PHP Editor that this should be a very important future enhancement. Still, this application offers a great deal of functionality at a very convenient price—it’s free. What’s more, there is no big corporate presence behind it, so that it really evolves following the needs of its users, and Davor does a great job of listening. php|a

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Performance Management Opportunities By Zeev Suraski and Brad Young Why Focus on Performance Management? A look at the various alternatives that exist in today’s complex IT world to improve server performance for sites that run PHP.

T

o start, let’s consider the reasons why we should be concerned with Performance Management. In a nutshell, it can be summarized with two simple goals: 1) Save Money 2) Happy Customers Although this may seem obvious, or even trite, it is important to keep in focus when evaluating and deploying performance-related products. To take it one level deeper, let’s understand the issues faced by IT managers and webmasters today:

· High expenses for hardware and software purchases to support http site traffic

· High expenses for database server hardware and software

· IT administration time and money spent to reconfigure and maintain server farms

· Low customer satisfaction resulting from unreasonable latency time and load time With these issues in mind, we can now more clearly attack the question of how to achieve improvements for our projects.

December 2002 · PHP Architect · www.phparch.com

As Yogi Berra famously stated, “It’s hard to make predictions, especially about the future.” For PHP, however, there are some things that are not so difficult to predict. Options For Performance Management There are many different ways through which you can squeeze more juice from your limited hardware server resources. These options include hardware, software, and networking alternatives. We’ll highlight each of these options below. Note that these alternatives are not mutually exclusive. Hardware Options

More Hardware - The most common indicator – aside from emails from angry site users – that raises a red flag about performance issues is maxed out CPU utilization. And when this happens, an obvious but costly solution is simply to buy more hardware. If you have two dual-CPU http server machines whose CPU’s

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are maxed out, then adding a third machine, with load balancing, will alleviate some of this load stress. It is worth noting that this solution works for steady state performance issues, but does not scale well for spiked performance issues. For example, if your site experiences dramatic increases in requests at specific times of the day, you’ll need to add enough hardware to cover the ‘worst-case’ load. (Actually, it is more accurate to call this the ‘best-case’. We want more traffic on our sites, after all.) Smarter Hardware – Similar to adding more hardware, adding smarter hardware can provide performance improvements. This includes the more obvious steps of having machines with faster CPUs, or more CPUs per machines. Beyond that, there is also hardware components such as disk drives with built-in memory caching that also help improve hardware performance. Hardware Devices – Another hardware option to improve performance is to utilize hardware devices that have built-in algorithm circuitry. For example, performing SSL encryption using software on your http server adds a significant stress to the CPU load. You can add a hardware card that performs this encryption without requiring any CPU time, thus lowering the effective load. Similarly, this can be done for gzip compression as well. Faster Code

It is clear that if your code is faster and more efficient, you’ll be able to handle more requests with the same hardware. Let’s explore how we can make code run faster. C Libraries– The massive adoption of PHP has come about mainly due to its ease of adoption – both from a cost perspective as well as a development perspective. But while PHP speed has improved tremendously, it is a fact that C code runs faster. So if you develop some of your more algorithmically-complex functions in C and call out to them from within your PHP scripts, you can speed up your code. Of course, by doing this, you give up some of the flexibility, transportability and ease of use that brought you to PHP in the first place. Write Better Code – Better coding practices, while tiresome at times to adopt, pay off in the long run. Always stay up to date and aware of the best ways to use PHP by following email lists from php.net and reading tutorial materials at sites like PHPbuilder.com and at the Zend Developer Zone (devzone.zend.com)—not to mention the pages of php|a, of course! Code Acceleration – PHP is an interpreted scripting language. This means that each time a PHP script needs to run, the core Zend Engine will parse that file and compile it in memory, then execute it. Since the PHP scripts themselves typically don’t change from December 2002 · PHP Architect · www.phparch.com

request to request, this parsing and compilation phase is repetitive and wasteful. Code Acceleration products available today can eliminate that redundancy by maintaining the compiled version of the file in memory. Output Content Caching

Imagine that your friend asked you what the headline of the New York Times was today. To respond, you go outside, walk two blocks to the nearest news-stand, read the headline of the New York Times, then come back and tell him what that headline says. (We leave it to you to understand why your friend would ask this, but just go with the analogy). Now, imagine that another friend calls you and asks the exact same question. Would you repeat the journey down to the news-stand? Unless you are madly in love with the salesperson, probably not. You are smart enough to identify that this new request is identical to the previous request, and hopefully you are also smart enough to remember what the headline was.

PHP is an interpreted scripting language. This means that each time a PHP script needs to run, the core Zend Engine will parse that file and compile it in memory, then execute it. Well, unfortunately your http server is not as smart as you, and it, figuratively speaking, is probably making way too many trips down to the news-stand (read: database server). This is where content caching comes in. The idea of content caching is straightforward: your server works hard to generate some results to a specific request. Then it keeps those results on hand, and if it gets a similar request, it re-uses the previously generated results. It is interesting to note that caching takes place at the http server level and reduces load on that server, but an even bigger load savings is experienced on the database server, which sees dramatically less SQL requests coming in. The concept is simple enough, but with all things programmatic, the devil is in the details. The challenge mainly boils down to: · Cache Hit Identification – How does the cache determine if this is indeed a similar request, or is it a different request (i.e. Is my second friend asking for the same headline, or is he asking

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Performance Management Opportunities Figure 1- Content Caching Schematic

about the New York Post, or is he asking about yesterday’s New York Times, or is the headline different for him because he gets the national edition instead of the local edition)? · Cache Management – How does the cache manage the information results that are onhand, purge old information, and prevent over-use of system resources (i.e. I can’t remember every headline of every newspaper from every day without my head exploding, so which is the best to forget)?

Now let’s look at a few ways of achieving content caching: File-level Content Caching – If you have web pages that appear the same to many users, you can store the entire results of the URL request coming in to your http server, as shown in Figure 1. For example, imagine a page that lists news headlines, such as cnn.com. New headlines are added, perhaps at a rate of one new headline per 15 minutes. CNN could cache the headlines page or at least 5 minutes. Now, if 1,000 page view requests come in during

Figure 2 - Partial Page Caching

December 2002 · PHP Architect · www.phparch.com

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that 5 minute period, only one actual PHP execution and one database access will occur, a dramatic decrease compared to the 1,000 that would otherwise occur. All the other requests are served directly from the cache, as if it was a static html file. And by having a time limit to this cached file, the worse case scenario Figure 3 - Database Intermediary

“Welcome, UserName” problem. In our headline listing page, the main portion of the page is the same for each user, but now we add a personalization message at the top of the page. We can no longer cache the entire file, unless we don’t mind that users named Judy, John, and Jade will get a page that says “Welcome, Joe”, the first person to request the URL.

PHP 5.0, with its new Zend Engine 2, will include new object handler capabilities that will not only make coding easier, it will also speed up application performance.

for content freshness would be that it would take a new headline 4 minutes and 59 seconds to make it to the site. When exploring solutions, you’ll want to make sure that there is sufficient flexibility for determining what should be considered a ‘cache hit’. Besides the basic URL address, you might also take specific cookie variables, GET parameters, or global http variables into consideration. For example, you might want to cache a different version of your home page for each geographic region, or type of user. Partial PageCaching – Solving the “Welcome, UserName” Problem– The benefits of file-level content caching are clear. But often, some portions of the page are personalized on a per-user basis. Let’s call this the

The solution here is partial page caching. We still can cache the majority of the page, which in this case also uses the most resource-intensive database queries. This is done at an API level, in which the caching of data segments is maintained and reused programmatically, as shown in figure 2. Database Intermediary Caching– A third option for caching of results involves separating your PHP code from the database, as shown in Figure 3. Instead, have a separate timed job that pulls content from the database and creates chunks of html files that the PHP scripts then can read in the output results that they are creating. This solution adds some complexity with regards to system configuration and code dispersal, but the results will sometimes make it worthwhile.

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Visit phplens.com for more details. Free download. December 2002 · PHP Architect · www.phparch.com

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Database Optimization

Data Models and SQL Tuning – As programmers, we often find ourselves focusing on our area of expertise – coding. However, even the fastest optimized algorithm as written in PHP can’t make up for the time wasted by poorly written SQL statements or queries to databases that are not modeled or indexed properly. Don’t fall into this trap. As mentioned earlier under the subject heading of “Write Better Code”, take the time to learn about how to get the most out of your database server. If you have a DBA in house, use his or her expertise. As with content caching, a little effort can go a long way when you tweak your database usage.

Also, identify the resources and infrastructure you have available. Once you measure these parameters, selecting the various products or methodologies mentioned above becomes much easier. Enterprise Performance – Future Directions As Yogi Berra famously stated, “It’s hard to make predictions, especially about the future.” For PHP, however, there are some things that are not so difficult to predict.

· First, Apache 2.0 adoption may start to grow,

Data Compression

Gzip Compression – “Performance problems” is a big umbrella. Sometimes, the performance issue is not necessarily server throughput or CPU utilization, but rather end-user experience of download time. Slow download may result from either large data transfer, or overutilization of server bandwidth. In both cases, you will improve end-user performance experience by compressing your data. Most browsers today can receive compressed contents, and will decompress automatically. Using output compression is as simple as setting zlib.output_compression = on in php.ini. Browser detection will determine if gzip support is built in, or if the original plain text should be sent. However, it is important to note that this adds some additional CPU burden to your server, which must perform a gzip compression for each result being delivered. This can be overcome by using a compression solution that is integrated with content caching. In this case, the compressed version is cached, and not regenerated each time. Network Infrastructure

While it isn’t directly related to PHP dynamic content, it is worth noting that network optimization solutions, such as those provided by Akamai , can boost content delivery time. This can be especially useful if image download and delivery time is your performance bottleneck. Which Should You Choose? As stated in the opening of this article, these options are not necessarily mutually exclusive. So, how do you make choices on how to boost your performance? Well, in the words of the anthropologist Margaret Mead, “Always remember that you are absolutely unique, just like everyone else.” First, identify what specific problems you are having.

December 2002 · PHP Architect · www.phparch.com

·

·

when the Apache stability as well as the PHP stability on top of Apache 2.0eventually reaches the necessary level. We may see some boosts to performance from Apache 2.0’s multithreaded capabilities, on platforms such as Solaris. PHP 5.0, with its new Zend Engine 2, will include new object handler capabilities that will not only make coding easier, it will also speed up application performance. In the database world, newer extensions and support for MySQL 4 and Oracle will likely give another shot in the arm for database throughput. Why Performance Management Matters

We opened this article explaining the benefits that Performance Management brings you and your organization: Save Money and Happy Customers. But the importance runs even deeper. Collectively, the PHP community is proving every day that PHP is ready for front-line, enterprise-level applications. Implementing performance management solutions such as those highlighted here bring us further towards the recognition from the marketplace that PHP is here to stay. php|a

Zeev Suraski has been working for over five years on the PHP project. Along with Andi Gutmans, he started the PHP 3 and 4 projects and wrote most of their infrastructure and core components, thereby helping to forge PHP as we know it today and attracting many more developers to join the movement. Zeev is a co-founder and CTO of Zend Technologies Ltd, the leading provider of development and performance management tools for PHP-enabled enterprises. Brad Young leads the Product Management team at Zend, and has over 15 years experience in on-line database and XML systems deployment. You can reach both Zeev and Brad via Zend's website at www.zend.com.

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Curses! Writing Cool Shell Applications With PHP By Marco Tabini While PHP is most widely used as a Web development language, I find that it works very well as a shell tool, too. In fact, I’d have to say that PHP is my favourite shell language, and that I prefer it over typical shells or even Perl (although the latter is rather unbeatable when you have to process large data files).

I

n a world of web-based management systems and graphical user interfaces, it’s comforting to find out that shell programming is still regarded as an important piece of the IT puzzle. Don’t get me wrong—I’m not saying this merely out of nostalgia for the times when I had to make do with 48kB of RAM for operating system, program and data, or had to wrestle a few cycles of program execution out of a mainframe. Text-based applications are still very useful in a number of situations, particularly when simplicity is called for or a GUI would be oppressively slow to deal with (such as when you’re trying to manage a web server that is heavily loaded and cannot spare much bandwidth for you). Shells, particularly (but not exclusively) in the UNIX world, are very much alive and kicking, and have advanced significantly in complexity and functionality over the past few years. nCurses - A Library For Cool Shell Apps Think “shell application” and the image of a dull, black-and-white text screen comes to mind. Luckily, most terminals are actually capable of a lot more than just displaying text: they provide a variety of colours and effects (such as underlined or bold—”bright”— text), mouse compatibility and much more. It’s normally rather difficult, however, to take advantage of these capabilities for a number of reasons. First, not all terminals are created equal—there are several different stan-

December 2002 · PHP Architect · www.phparch.com

dards available, each with its own commands and capabilities. Second, because terminal systems have to work over simple serial communication lines, the commands they support are often intricate combinations of ASCII characters. Since shell applications are usually written as a quick and easy solutions to simple problems, the developers rarely have the time and patience to bother with adding the “frills” to their interfaces. Those of you who, like me, have spent their youth wasting their allowances on telephone bills as a result of the expensive hobby known as “BBS”, however, know what terminals are capable of. Remember the cool menus, the dazzling animations and the colourful interface? Compare that with your average shell application and, well, I’d take the BBS over it every day. On UNIX systems, the capabilities of terminals are stored in the termcap database, a file usually found in the /etc directory that is used by applications such as the original vi editor. Termcap contains a description of each terminal that is recognized by the system (for example, “dumb” or “ansi-compatible”), together with the commands it supports. Termcap, however, is not in a very “developer-friendly” format. In fact, I think it’s fair to say that using it in REQUIREMENTS PHP Version: Latest PHP CVS Build O/S: nCurses-compatible O/S Web server: N/A Support Tools: nCurses Library

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Curses! Writing Cool Shell Applications With PHP

an application with no outside help would require a major effort, since you would only have to interpret its contents, but also write the necessary functions to handle tasks like cursor positioning, text attributes, window management, and so on. It was probably out of desperation that, around 1980, a student at UC Berkley named Ken Arnold developed a series of routines that provided an essential framework for terminal interface development and collected them in what became known as the “curses” library. Curses then became the basis for Rogue, possibly one of the first-ever Role Playing Games, initially developed for BSD Unix but eventually ported to pretty much any operating system ever conceived. If you have never played Rogue, I suggest you give it a try— not only it’s a thoroughly enjoyable and never repetitive game, but it also gives you an idea of how engaging a simple text-based user interface can be. You can find Rogue in RPM format at : http://www.rpmfind.net/linux/rpm2html/ search.php?query=rogue I should warn you that you will find it highly addictive; your productivity will probably drop to zero for a while, but you’ll have lots of fun in the bargain.

• When you need to deploy a web-serving framework capable of delivering millions of views and transactions per day... • When you need to construct complex document and task workflows that match your organizations' needs... • When you need to create a world wide streaming network capable of 99.99% up time... • When you need to protect your country's sovereignty by avoiding "random" changes in software licensing that can affect the price of each transaction your citizens make... • When you need the level of security that only expertise and transparency can provide you...

The Curses library was picked up by Bell Labs, which included it in its System III version of UNIX, introducing several changes to termcap in the process. Termcap’s new format, called terminfo, offered more functionality. Additional development was done through the 1980s, and in 1993 the package was finally renamed ncurses. Ncurses and PHP The ncurses library provides a number of features, such as: · Formatted input and output on a variety of terminals · Support for colours and various text styles, such as underline, bold, and so on · Support for windowing · Support for mouse input PHP support for the ncurses library is still very much in its infancy, and is based on the GNU implementation of the library, available via FTP at: ftp://ftp.gnu.org/pub/gnu/ncurses

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FEATURES It was originally introduced by Hartmut Holzgraefe and Georg Richter with version 4.1.0 of PHP and is still considered highly experimental, to the point that the official PHP documentation covers the ncurses functions only very quickly and in a still incomplete fashion. Luckily, the ncurses extension functions follow their original counterparts very closely, which actually makes the process of creating an ncurses-powered PHP script very easy (this is something that the authors of the extension must have undoubtedly known, so that they have—correctly, in my opinion—put all their efforts in building out the extension). Ncurses is actually supported on a number of platforms, including all the UNIX derivatives, cygwin and BeOS. Obtaining the Right Version of PHP The problem with making ncurses run on your server is that, in order to gain access to enough functionality, you will have to download the most recent version of PHP from the public CVS tree. There is no way around this problem, as the stable releases available to this point do not yet include the latest code, which is unfortunately necessary to perform most of the basic ncurses tasks. Luckily, obtaining the latest version of PHP is not difficult at all. You can get it directly by issuing a couple of CVS commands, which are clearly explained in the manual:

cvs -d :pserver:[email protected]:/repository login cvs -d :pserver:[email protected]:/repository co php4

If all goes well, you should end up with a sub-folder of your current directory called php4. Simply cd into it and configure PHP as you would normally, ensuring that you include --with-ncurses to your invocation of configure, and that you compile the CLI version of PHP—after all, I’m afraid that you would have little use for the ncurses extension in a web application. Our First ncurses Application It’s now time to test whether the installation went smoothly by executing the simple PHP script that you can see in Listing 1. This script is designed to be run from the shell. As such, it includes a “shebang”, that is, a specially-formatted comment (always the first line of the script), that instructs the shell as to which interpreter this file should be executed through. This approach works only on UNIX-type shells, however, so if you’re running Windows you’ll have to use the cygwin shell rather than the DOS command prompt. December 2002 · PHP Architect · www.phparch.com

Curses! Writing Cool Shell Applications With PHP If you do not receive any errors, you should see the words “Hello World!” written in red text over a cyan background appear at the top of your screen for a few seconds and then disappear. If something goes wrong, there’s a good chance that your shell will become unusable—don’t panic, this is quite normal, as we’ll see in a few moments. As you can see, even a simple Hello World application requires quite a bit of code if you write it using ncurses. You not only have to initialize the library using the ncurses_init() function, but you have to create a combination, or “pair”, of each foreground and background colours that you want to use in your application. This, in turn, will only work if the terminal you are using supports colours to start with, and the ncurses_has_colors() function provides the script with that information. Even writing a string to the screen requires a call to a specialized ncurses function, ncurses_addstr(). The latter is actually part of a family of functions that make it possible to manipulate text on the screen. Incidentally, you will also have noticed that it’s necessary to forcefully refresh the screen in order for any updates made to it to become visible. This particular aspect of ncurses programming is actually designed so that only the minimum amount of commands are sent to the screen, and only when necessary—thus reducing the amount of data sent to the terminal by as much as possible. With today’s fast connections, this may sound a bit ridiculous, but you have to understand that ncurses must be able to work efficiently even over slow serial connections—and a bit of optimization never hurts. Thus, for the most part, an application writes to a “virtual screen” and then issues a call to ncurses_refresh() when all of its updates are complete and it is ready to show its output to the user. Finally, the ncurses library must be explicitly terminated by calling ncurses_end(). This is necessary because ncurses captures the terminal and creates its virtual screen over it. As a result, exiting from a script without also terminating ncurses results in a terminal that, in most cases, is completely unusable. The problem of course, is that sometimes scripts end unexpectedly, as it is often the case when errors occur. For this reason, it’s always a good idea to create your own error handler that explicitly calls ncurses_end() before aborting your script. This will not protect you from all kinds of problems (parse errors will still cause PHP to exit without calling your handler, for example), but it will take care of at least some cases. With the exception of windowing functions, which we’ll examine in the next section, all ncurses functions return true if an error has occurred (they actually return an integer value different from NCURSES_ERR, which is defined as zero).

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Curses! Writing Cool Shell Applications With PHP Windowing

One of the most interesting characteristics of ncurses is the ability to create and manage multiple windows. Although they cannot overlap each other, each window possesses its own “virtual screen” and can be modified and refreshed independently of its other counterpart on the terminal. As an example, let’s take a look at Listing 2, which introduces a number of new ncurses functions. The first one is ncurses_getmaxyx(), which returns the dimensions of the virtual screen. You have probably noticed that, in this function, the height is listed in the function call before the width—something that may appear unnatural to someone who is used to working with GUI systems. All ncurses functions follow this convention, however, and it does take a while to get used to it. Also, the call to ncurses_getmaxyx() at the beginning of Listing 2 uses a constant called STDSCR. This constant describes, by convention, a pointer to the main virtual screen, which is, for all purposes, a window of its own right. In fact, most of the ncurses functions that manipulate the virtual screen also have a windowspecific counterpart—for example, ncurses_addstr() and ncurses_waddstr(). In most cases, the ncurses library implements the virtualscreen version of these functions as simple macros to the window versions with the hardcoded STDSCR parameter. The ncurses_newwin() function is used to create a new window. Its syntax is as follows: resource ncurses_newwin ( int $height, int $width, int $y, int $x );

Its result is an ncurses resource that you can use in subsequent calls to other ncurses functions that can manipulate the contents of your newly created window, such as ncurses_wborder, which—you guessed it—creates a border around the frame of our window: int ncurses_wborder ( resource $win_resource, int $left_side, int $right_side, int $top_side, int $bottom_side, int $top_left_corner, int $top_right_corner, int $bottom_left_corner, int $bottom_right_corner );

December 2002 · PHP Architect · www.phparch.com

With the exception of the first parameter, which identifies the window where the border is to be drawn, each of the other parameters represent the characters that the function must use to build the border. If you leave all these parameters as NULL or zero, ncurses_wborder() will create a standard (and classy) border around the window. If, for example, you call the function as follows: ncurses_wborder ( $win1, ‘|’, ‘|’, ‘-’, ‘-’, ‘+’, ‘+’, ‘+’, ‘+’ );

You will obtain a slightly less pleasant—but just as functional—border. Writing into a window is performed through a number of functions. The simplest one is ncurses_waddstr(), which is functionally equal to ncurses_addstr(), with the exception that it takes a window resource as the first parameter. In the case of Listing 2, however, I have used a slightly more complex version of it called ncurses_mvwaddstr(), which at the same time moves the cursor to a pre-defined position and prints out the string passed to it: int ncurses_mvwaddstr ( resource $win_resource, int $y, int $x, string $str );

As you may have noticed, the x and y coordinates passed to this functions reference the top-left hand corner of the window—not of the screen. There is, naturally, an equivalent of ncurses_mvwaddstr() that works with the virtual screen and is called ncurses_mvaddstr(). This, in turn, is functionally equivalent to calling ncurses_mvwaddstr() as follows: ncurses_mvwaddstr ( STDSCR, $y, $x, $str );

Finally, we come to the visualization of windows, which is achieved by calling the ncurses_wrefresh() function. Keep in mind that ncurses does not handle windows the same way a GUI system like

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FEATURES Windows or XWindows would; this means that the overlapping of windows and features like z-order are not normally provided to the developer (although another portion of ncurses called panels, which is also being implemented in the PHP extension, does provide exactly this functionality). Thus, wrefresh() should simply draw a particular window on the screen, as if it were in focus and with complete disregard for whatever other windows may overlap with it. I say “should” because in reality different versions of ncurses behave in different ways—as such, it’s best to either use only tiled windows, or to use one window at a time on top of the virtual screen. Thus, calling wrefresh() will cause a window to be drawn ontop of the virtual screen, in our cases advising us that its contents are rather messy. Another interesting characteristic of ncurses is that it provides no scrolling capabilities. When you reach the end of the screen (or of a window), text is simply discarded. Depending on the type of application that you are writing, this could be a major problem—but it can be easily solved as we’ll see later on. A Bit of Colour and a Sprinkle of Fairy Dust As marketing people have known for years, colour makes all the difference. In a well-designed interface, proper colour management can make any application easier to use (except for vim, which was obviously written by aliens) and more pleasant to the eye. The ncurses library provides an extensive set of functions that deal with the aspect of text—not only with its colour, but also with its intensity and style. For example, Listing 3 produces text in quite a variety of styles. Because colours can only be rendered on some terminals, the ncurses extension provides the ncurses_has_colour() function to determine whether colours can, in fact, be used on the current terminal. Also, colour rendering has to be enabled by calling the ncurses_start_color() function. The ncurses library, as I mentioned above, handles colours by means of “pairs”, each representing the combination of a foreground and background colour. Each pair is defined using the ncurses_init_pair() function: int ncurses_init_pair ( int $pair_id, int $foreground_colour, int $background_colour );

The ncurses extension provides a number of pre-set colour definitions, which are shown in Figure 1. On some terminals, it is also possible to create custom December 2002 · PHP Architect · www.phparch.com

Curses! Writing Cool Shell Applications With PHP colours by changing the RGB values associated with a particular pre-defined colour (you could finally have your own opportunity to invent the “greenest blue” ever made!) through a call to ncurses_init_color(), whose syntax is as follows: int ncurses_init_color ( int int int int );

$color, $rgb, $green, $blue

A call to ncurses_can_change_color(), which takes no parameters, will tell you whether you can, indeed, change the appearance of a particular colour. Figure 1 NCURSES_COLOR_BLACK NCURSES_COLOR_WHITE NCURSES_COLOR_CYAN NCURSES_COLOR_RED NCURSES_COLOR_YELLOW NCURSES_COLOR_BLUE NCURSES_COLOR_MAGENTA NCURSES_COLOR_GREEN

Black White Cyan Red Yellow Blue Magenta Green

Attributes are handled in a very similar fashion to HTML. They can be turned on using the ncurses_attron() function (or ncurses_wattron() for a window), or off through a call to ncurses_attroff(). A list of available attributes is shown in Figure 2. Figure 2 A_NORMAL A_STANDOUT A_UNDERLINE A_REVERSE A_BLINK A_DIM A_BOLD A_PROTECT A_INVIS

Normal font Standout (reverse) Underlined Reverse screen Blinking Text Dimmed Bold Protected Invisible

Similarly to colours, there is a way to determine whether a particular attribute is supported by the current terminal. The ncurses_termattrs() function takes no parameter and returns a logical OR of all the attribute values that the terminal can handle.

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Curses! Writing Cool Shell Applications With PHP Listing 1

1 #!/usr/local/bin/php 2 3

Input Management As I’m sure you can imagine, a good user interface without input capabilities is a bit like a war with no enemy—you could make one but it would be rather dull and quite pointless. The ncurses library offers a number of facilities for both keyboard and mouse input, although we will only focus on the latter as far as this article is concerned. The most commonly used form of keyboard input is ncurses_getch(), which retrieves a single character from the input stream. Under normal circumstances, that character is also outputted to the screen, but you can prevent that from happening by calling the ncurses_noecho() function. For example, take a look at Listing 4, which shows a simple script that can be used to control the Apache web server through a series of simple commands. As you can see, there are a couple of interesting functions. First, I’ve created a simple msgbox() routine

December 2002 · PHP Architect · www.phparch.com

that takes an arbitrary amount of text and displays it in an ordered fashion on a window of its own. This corresponds to a simple dialogue window in a GUI environment. You will notice that I have used the wordwrap() function to ensure that the text is always properly centered and never interferes with the window’s borders. The lack of a couple of ncurses functions (in particular wsyncup() and wsyncdown()) in the PHP extension make it slightly awkward to manage windowing properly, so that the application is forced to manually refresh the screen every time a dialogue box is displayed. The ncurses_getch() function is called in an infinite loop until the user presses the “q” key and exits. The result value of ncurses_getch() is not, however, a character, but an integer value. This lets you manage “special” characters, such as Page-up and Pagedown, more easily and conveniently—but you will have to convert the integer value to a string if you want to interpret it as a character. More complex input can be

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Curses! Writing Cool Shell Applications With PHP

performed by calling the ncurses_instr() function, which reads an entire string from the input and returns it. It’s interesting, at least in my opinion, to note that even a simple script like this one can be set as the default command for a particular user account, thus depriving it of shell access but still giving it the opportunity to perform certain operations—in this case, stopping and starting Apache. A More Complex Example Let’s now move on to a more audacious attempt at using the ncurses library to produce a complete shell-

based application. Listing 5 contains a self-contained text file viewer that allows for up and down scrolling (both line by line and page by page), can split and display lines of text that span multiple lines (without using wordwrap, this time) and displays a status line at the bottom of the screen. This script introduces the ncurses_move() function, which is used to move the cursor to a particular location (in fact, ncurses_mvwaddstr() is essentially the equivalent of a call to ncurses_move() followed by a call to ncurses_waddstr()). You’ll notice that the most complicated action performed by this script is the tracking of the position of the screen’s output within the text file. For the script to

Listing 2 1 #!/usr/local/bin/php 2 3
Continued On Page 21...

December 2002 · PHP Architect · www.phparch.com

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Curses! Writing Cool Shell Applications With PHP

stop scrolling at the end of the file, it is necessary to track both the position within the file that corresponds to the top of the screen (which we need so that we can refresh it), as well as the position that corresponds to the bottom of the screen. This is made more difficult by the fact that there is no direct correspondence between the width of the screen and the length of each line of text, so that a single line of text can in fact correspond to multiple lines on the screen—but we still want the script to scroll by one screen line at a time, so that the script has to track the correspondence between screen display and file. To make things a bit easier, I have separated the file in its individual lines by using the file() function. Clearly, it would have been much simpler to load the file in memory and then use wordwrap() on it to

Listing 2: Continued From Page 20... 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

// Refresh the window, thus making it visible ncurses_wrefresh ($win1); // Wait a while sleep (2); // Destroy the window ncurses_delwin ($win1); // Exit ncurses_end(); ?>

Listing 3 1 #!/usr/local/bin/php 2 3
December 2002 · PHP Architect · www.phparch.com

Continued On Page 24...

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Curses! Writing Cool Shell Applications With PHP

ensure that there would be a one-to-one correspondence between the screen and the file. However, you can take this script and turn it into a full-fledged editor with relatively minor modifications—whereas if it were based on the wordwrap() trick it would be much more difficult to do so.

CVS tree of PHP, while there is no support for the form library. However, they are both very important, as they can greatly simplify the development of complex shellbased applications. For an example of their full capabilities, take a look at the Lynx text-based web browser, which uses both libraries to their fullest potential.

Where To Go From Here There is much more to the ncurses library than what we’ve been able to explore here. In particular, recent versions of ncurses include two libraries, panels and form, that can be used to manipulate overlapping (and scrollable) windows and form fields respectively. The panels library is already partially implemented in the

php|a

Marco Tabini is co-editor of php|architect. He spends most of his time lurking around on the PHP mailing lists and on the php|a website doing is best to confuse fellow programmers who are in trouble. You can reach him at [email protected].

Listing 4 1 #!/usr/local/bin/php -q 2 3 (strlen ($text) + 4)) 40 $win_w = strlen ($text) + 4; 41 else 42 $text = wordwrap ($text, $win_w - 4); 43 44 $string_data = explode ("\n", $text); 45 46 if ($win_h > (count ($string_data) + 4)) 47 $win_h = count ($string_data) + 4; 48 49 // Create a new window 50

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Curses! Writing Cool Shell Applications With PHP Listing 4: Continued From Page 22...

51 $win = ncurses_newwin ($win_h, $win_w, ($height - $win_h) / 2, ($width - $win_w) / 2); 52 53 // Apply a simple border 54 55 ncurses_wborder ($win, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL); 56 57 // Type all the information 58 59 for ($i = 0; $i < min ($win_h - 4, count ($string_data)); $i++) 60 ncurses_mvwaddstr ($win, $i + 2, ($win_w - strlen ($string_data[$i])) / 2, $string_data[$i]); 61 62 // Refresh window 63 64 ncurses_wrefresh ($win); 65 66 // Wait for input 67 68 ncurses_getch(); 69 70 // Destroy window 71 72 ncurses_delwin ($win); 73 } 74 75 // Creates the main menu 76 77 function main_menu() 78 { 79 // Clear screen 80 81 ncurses_erase(); 82 83 // Create main menu 84 85 ncurses_color_set (2); 86 ncurses_attron (NCURSES_A_BOLD); 87 center_window (STDSCR, 2, "Main Menu"); 88 center_window (STDSCR, 3, "---------"); 89 ncurses_attroff (NCURSES_A_BOLD); 90 91 center_window (STDSCR, 4, '(1) Stop Apache'); 92 center_window (STDSCR, 5, '(2) Start Apache'); 93 center_window (STDSCR, 6, '(3) Restart Apache'); 94 center_window (STDSCR, 8, '(Q) Quit'); 95 96 ncurses_refresh(); 97 } 98 99 // Initialize ncurses 100 101 if (ncurses_init()) 102 die ("Unable to initialize ncurses!"); 103 104 // Initialize colour, if available 105 106 if (ncurses_has_colors()) 107 { 108 // Initialize a simple colour pair 109 // And select it 110 111 ncurses_start_color(); 112 113 ncurses_init_pair (1, NCURSES_COLOR_CYAN, NCURSES_COLOR_BLACK); 114 ncurses_init_pair (2, NCURSES_COLOR_RED, NCURSES_COLOR_BLACK); 115 } 116 117 // Turn off echo 118 119 ncurses_noecho(); 120 121 // Create main menu 122

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Curses! Writing Cool Shell Applications With PHP LISTING 3: Continued From Page 21...

50 51 52 53 54 55 56 57 58 59 60 61 62

// Refresh the screen ncurses_refresh(); // Wait a while sleep (4); // Exit ncurses_end(); ?>

Listing 4: Continued From Page 23... 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155

main_menu(); while (true) { $c = ncurses_getch(); $s = chr ($c); switch ($s) { case '1' : msgbox (shell_exec ("apachectl start") . "\n\nPress a key to continue"); main_menu(); break; case '2' : msgbox (shell_exec ("apachectl stop") . "\n\nPress a key to continue"); main_menu(); break; case '3' : msgbox (shell_exec ("apachectl restart") . "\n\nPress a key to continue"); main_menu(); break; case 'Q' : case 'q' : ncurses_end(); exit; break; } } ?>

December 2002 · PHP Architect · www.phparch.com

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SNMP Management With PHP By Harrie Hazewinkel In the last decade, the importance of distributed services has become clear, as organizations have deployed networks to automate their business processes. As a result, organizations now depend on their networks and the related services, and any minute of down-time costs money. Not only personnel cannot perform their work during down-time, but many automated services, such as telesales, for instance, stop working. If an organization monitors its network, it can detect problems before they become a problem, increasing productivity and reducing personnel costs. This article provides a brief explanation of the SNMP protocol and explains the SNMP functionality that is available through PHP.

Simple Network Management Protocol

T

he Simple Network Management Protocol (SNMP) provides a framework for network management. SNMP enables access to network management information to make, for instance, status monitoring, faultdetection and configuration possible. Since its introduction, SNMP has been used heavily to perform monitoring and fault detection tasks. There has been little use of SNMP for configuration purposes, though, since it lacks a proper security protocol. However, the latest SNMP framework (version 3) defines security functionality by means of authentication, privacy and access control. These features protect the network against threats such as: 1. Modification of an SNMP message in transit by an unauthorized SNMP entity. 2. Modification of the SNMP message stream by changing the order, delaying or replaying messages. 3. Masquerading of SNMP entities through the appropriation of another SNMP entity’s identity. 4. Disclosure of management information that is December 2002 · PHP Architect · www.phparch.com

transferred between SNMP entities (users). 5. Eavesdroppers that attempt to capture the management data for other “evil” purposes. 6. Unauthorized access to particular management information. If you compare these capabilities with earlier version of SNMP, which only offered a single clear text password authentication method and no encryption, you’ll see that SNMPv3 represents a big step forward for the protocol’s security features. What’s more, SNMPv3 defines three different security levels: 1) No authentication and no privacy 2) Authentication and no privacy 3) Authentication and privacy It also allows for the use of different authentication and privacy protocols, thus enabling SNMP to evolve over time as new and better security mechanisms are REQUIREMENTS PHP Version: PHP 4 (4.3.0 for SNMPv3 support) O/S: Any Web server: Any Support Tools: N/A

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SNMP Management With PHP Figure 1

defined. The SNMP framework

An SNMP manager requests management information from an SNMP agent. The manager invokes an SNMP request on an agent and the agent collects the requested information from its MIB and produces a response for the manager. The manager interprets the returned information and can use it for logging, status reporting or for automated actions. like initiating alarms. A typical example of this would be a polling system in which periodically traffic counters are collected by the SNMP manager.

Figure 2

An SNMP agent initiates a notification to a manager. Notifications are used when an agent detects an unusual or anomalous situation on its own, such as when an interface on the host goes down. Upon detecting the fault, the SNMP agent informs directly the SNMP manager of it, so that the latter can take the appropriate action, such as initiate an alarm.

Figure 3

December 2002 · PHP Architect · www.phparch.com

SNMP is built around an asymmetrical framework of many SNMP agents and one (or a few) SNMP managers. An SNMP agent resides in a remote host or device and is connected to the actual hardware that needs to be monitored. It provides access to the hardware via managed objects through an interface known as Management Information Base (MIB). The agent responds to queries from managers that request information from its MIB. A manager can therefore create a complete and coherent picture of the network’s status by requesting specific management information from multiple agents. The Management Information Base The Management Information Base (MIB) contains the managed objects under management by an agent. Briefly explained, the MIB is a virtual information store composed of one or more MIB modules. Each MIB module implements a specific set of management information, which is itself organized in an ordered tree. Only the leaves of this tree can contain real data, and then only if the object/node is defined as an ‘OBJECTTYPE’ (we’ll get to that in more detail later). The intermediate nodes used for creating the hierarchy do not actually contain any information, but provide the tree with a logical structure. Figure 3 illustrates an MIB tree example that is a part of the SNMPv2-MIB as defined in RFC 1907 (which can be downloaded from http://www.ietf.org/rfc/rfc1907.txt, if you’re interested in reading the complete MIB module specification). The tree depicted in this snapshot contains three objects (sysName, sysContact and sysLocation) representing scalar variables, as well as two objects ordered in a table under the sysOREntry node. The table objects are ordered by column (sysORID and sysORDescr), while each row is uniquely identified by an index. The indexes used in Figure 3 are 2 and, therefore, the table contains 4 values (2 columns * 2 rows). Each node in the MIB tree has a human readable name and is ordered by number. A specific node is described by an Object Identifier that combines the numbers of the branches along the path starting from the root. To find a particular leaf in the MIB, both an exact and a next search can be performed. The exact search requires that the name of the leaf being searched for exactly match what is saved in the data store, while the next search returns the first lexical graphical higher leaf. Figure 3 depicts a sample walk. Each arrow indicates

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FEATURES the “next” of a particular object. To indicate that there are no more “next” values in the MIB tree, an exception called ‘EndOfMIBView’ is used. Structure of Management Information The language in which MIB modules are written is called Structure of Management Information (SMI). SMI was originally based on the Abstract Syntax Notation 1 (ASN.1). Let’s take a look at a small portion of this language - just enough to understand the creation of an MIB tree. The entities defined in a tree must all conform to the following standard format: ‘::=’ ‘{‘ ‘}’

The is used as a human readable identification of the object/node in the MIB tree. The provides specific information of the object. In the excerpt, all three definitions are of the ‘OBJECTTYPE’ kind, which includes the syntax of the object, the type of access granted to it (read/write), its status and its description. The provides the hierarchy information. Typically it consists of a single name and a single number. The name indicates the parent node in the MIB tree and the number indicates the current position in the tree with respect to its ancestors. For example, in Figure 3, the definitions of ‘system’ has the number 1 and the parent node is ‘mib-2’. The ‘sysContact’ entity defines the contact information of the particular system on which the MIB is defined, as mentioned by its ‘DESCRIPTION’ parameter. Its parent node is ‘system’ and its own numerical identifier is 4. SNMP and PHP After having guided you through a brief introduction to SNMP and its management framework, it’s now time to talk about the functionality of the SNMP extension in PHP. The PHP extension has been part of PHP for a long time, and it was originally developed by Rasmus Lerdorf as the UCD-SNMP module. At that time it supported the cutting edge version of SNMP—version 1. Over time, minor modifications have been made to extension, mainly due to changes in the packages it depends on, and it is currently called NET-SNMP. Some 3 years ago, I wrote an SNMP extension that made it possible to take advantage of the security features that are part of SNMP version 3. This was never included in the main distribution for various reasons. However, ever since I returned to Europe and went to live in Italy, I started working on the extension again and have included the security features of SNMP version 3 in the main distribution for the next release of PHP. December 2002 · PHP Architect · www.phparch.com

SNMP Management With PHP As we have seen in the previous section, SNMP activities can really be divided in two kinds of operations: retrieving information on request from the manager’s side and initiating notifications from the agent’s. The PHP language only supports the first form. This is mostly for historical reasons, since the first versions of PHP were used as scripting tools for web-based systems in which a notification from the client would simply have been impossible to implement: PHP scripts in web pages are only executed upon a web client’s request, and this methodology obviously does not allow for a continuous listening for notifications. In addition, the probability that a notification be received exactly when a web page is requested is pretty much zero. Thus, the only SNMP-related commands available in PHP are management information-related. Generally they can be used in polling operations. PHP-SNMP functions The SNMP functions in PHP can be divided into two groups, helper functions and protocol functions. The protocol functions that we discuss here are those that exist in versions of PHP that have already been released, and are based on SNMPv1, as are the example scripts. However, the upcoming new release of PHP (4.3) will include the new SNMPv3 functions and will support the new protocol security features. These new functions are discussed later in this very article. Helper functions The helper functions (Figure 4) are used only to alter the format in which the values passed to and from the protocol functions are used. These functions are only for internal use and do not communicate to external SNMP agents. The only parameter that they accept is a boolean that indicates whether a particular feature is to be used or not. The example shown in Listing 1 illustrates a script in which the helper functions are used to change the output resulting from calls to the protocol functions. Their output is shown in Figure 5. Protocol functions The protocol functions (Figure 6), on the other hand, are used to communicate with the remote SNMP agents. They are all used for data retrieval, except for snmpset(), which can change management data in a remote SNMP agent. These functions almost all take the arguments shown in Figure 7 Listing 2 provides an example of how these functions can be used in a real-life scenario. I have commented the script in detail to make it easier for you to follow it. SNMP In Practice Now that we have introduced all of PHP’s SNMP

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SNMP Management With PHP Listing 1

1

functionality, we’ll take a look at a few examples to show how scripts that allow polling of network management data from a remote SNMP agent can be written. For our first example, we want to create a script that provides generic system data about the remote server, such as its hostname (sysName), its location (sysLocation) and the person responsible (sysContact) for its administration. These are the managed objects that we have used earlier to explain the MIB tree and the MIB module syntax. Listing 3 contains two approaches that achieve this result in two different ways. The first method consists of a series of explicit calls to snmpget() to retrieve the required information from the remote SNMP agent. This results in 3 requests on the wire. The second approach, on the other hand, is based on an MIB branch retrieval and subsequent filtering of the information needed. This last method results in a high number of requests being made to the agent, and does not represent the optimal solution to the problem, since the entire information tree is retrieved, even though only three of its values are actually needed. The output of Listing 1 is shown in Figure 8. The Interface table The second example, shown in Listing 4, retrieves some columns from a table and demonstrates how Figure 4: Helper Functions bool snmp_get_quick_print (void) void snmp_set_quick_print (bool quick_print)

indexes are used. The table whose values are being outputted is the interface table, or “ifTable”, which is December 2002 · PHP Architect · www.phparch.com

defined in the IF-MIB module published in RFC 2863 (available at http://www.ietf.org/rfc/rfc2863.txt). This table maintains information about the interfaces in a system; an interface is defined as an entry point to the next underlying layer in a protocol stack. A common example of this is the TCP/IP stack in network interfaces and serial line connectors. The New SNMPv3 Functions Recently, I have added new functionality to the SNMP module so that it can support the SNMP version 3 specifications and, in particular, its security model. All the protocol functions available in the SNMPv1 module have an equivalent in SNMPv3. The only difference between the new functions and the old ones is that their ‘snmp’ prefix must be changed into ‘snmpv3’. Also, the community password string used for SNMPv1 must be replaced by the parameters shown in Figure 9. As you can see in Figure 10, upgrading current scripts to SNMPv3 is very easy—all you have to do is change the function names and introduce the new security parameters. The PHP team took this approach to encourage all developers to upgrade their scripts and deploy the new security features for the management of their systems. The next release of PHP will also contain two new SNMP helper functions shown in figure 11. I introduced them as solutions to problems I encountered trying to interpret object identifiers and enumeration values in my scripts. The first function, snmp_set_enum_print(), causes the module to manipulate the data produced by SNMP agents so that, if it is part of an enumeration, its “human readable” value will be returned rather than its numeric one. The second, snmp_set_numeric_print(), causes values

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Figure 5 sysName (quickprint default/’’):STRING:orville.cardano.lisanza.net sysName (quickprint ‘1’) :orville.cardano.lisanza.net sysName (quickprint ‘’) :STRING: orville.cardano.lisanza.netharrie@orville$

Listing 2 1

December 2002 · PHP Architect · www.phparch.com

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SNMP Management With PHP Figure 6: Syntax Protocol Functions

string snmpget (string target, string community, string object_id [, int timeout [, int retries]]) array snmprealwalk (string target, string community, string object_id [, int timeout [,int retries]]) bool snmpset (string target, string community, string object_id, string type, mixed value [, int timeout [, int retries]]) array snmpwalk (string target, string community, string object_id [, int timeout [, int retries]]) array snmpwalkoid (string target, string community, string object_id [, int timeout [, int retries]])

returned by a SNMP agent in numeric format not to be converted into human readable format. Numeric values are probably less intuitive to use for developers, but they possess the great advantage of remaining constant Figure 8 Explicit requests (SNMP-GET) The system name is: STRING: orville.cardano.lisanza.net The system administrator is: STRING: <[email protected]> The system location is: STRING: Cardano,Italy Tree retrieval, value selection (SNMP-WALK) The system name is: STRING: orville.cardano.lisanza.net The system administrator is: STRING: <[email protected]> The system location is: STRING: Cardano,Italy

and not being subject to change when moving from one system to another. Tips and tricks Many people dislike SNMP mainly because the do not understand how to read MIB modules or because they claim to have too little control over the SNMP

agent. Here are a couple of tricks that can make your life as a script developer a bit easier. 1) Determine first what you want to monitor from a high-level perspective and what is important for your deployment. This provides you as a developer with better guidance and direction and helps not to get lost in the SNMP details. 2) Use tools like libsmi (also open-source, and available from http://www.ibr.cs.tu-bs.de/projects/libsmi) that can help you by building an MIB tree for your viewing pleasure. If you use the ‘-f tree’ option, smidump will create a summary representation of the MIB modules that are part of a particular tree. This will enable you to determine the complete identifier of any object quickly and efficiently. 3) Use snmprealwalk() on your target agent as a tool to help you determine the identifiers of the objects you need. If you print out the results of a snmprealwalk() call, you can see what the human-readable form of a particular object identifier is. 4) Although this requires a bit more detailed knowledge of SNMP and MIB modules, use the numeric form of the object identifiers and the new snmp_set_numeric_print() function to retrieve the numeric form of your object identifiers. The advan-

Figure 7

string target

The target is used to define the hostname or the IP address of the remote SNMP agent as well to indicate the port (default 161) number the SNMP agent listens. Some examples are: “hostname” or “hostname:1661” where the first uses the default port number and the last the port number 1661 for the SNMP agent on the system ‘hostname’.

string community

The community string is an identification of the user/system that wants to access management information in an SNMP agent.

string object_id

The object identifier indicates the management information that is requested from the SNMP agent.

int timeout

The time out after which the SNMP request is resend if no reply is received.

int retries

The amount of retries that must be made before giving up.

string type and mixed value (only used for the snmpset)

The type and the value to which the object identifier in the remote SNMP agent will be set.

December 2002 · PHP Architect · www.phparch.com

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SNMP Management With PHP Listing 3

1

Figure 9 string username

The username identifies who wants access a remote SNMP agent. This could be compare to the old community string of SNMPv1/v2C. The security level defines the grade of security and only the following levels exist:

string sec_level

- ‘noAuthNoPriv’ or ‘nanp’; a security level that is similar to community-based security. This level does not require any of the authentication and privacy parameters to be set and therefore must be provided as “” empty strings. - 'authPriv' or 'ap'; the highest security level that provides authentication and encryption. This level does require both the authentication and the privacy parameters to be set.

string auth_protocol

The authentication protocol defines the sort of authentication used. The following protocols are supported 'MD5' and 'SHA'

string auth_passphrase

The authentication passphrase is used to generate an authentication key with which the authentication is done.

string priv_passphrase

The privacy protocol defines the encryption protocol and the following protocol is currently only supported ‘DES’.

string priv_passphrase

The privacy passphrase is a secret phrase to be used to generate an encryption key.

December 2002 · PHP Architect · www.phparch.com

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SNMP Management With PHP Listing 4

1 \n"; 47 echo "\n"; 48 echo "Interface\n"; 49 echo "Description\n"; 50 echo "Type\n"; 51 echo ""; 52 for (reset($ifIndex); $oid = key($ifIndex) ; next($ifIndex)) { 53 $i = $ifIndex[ $oid ]; 54 echo "\n"; 55 echo "" , $i , ""; 56 echo "" , $ifDescr[$i] , ""; 57 echo "" , $ifType[$i] , ""; 58 echo "\n"; 59 } 60 echo "\n"; 61 ?>

tage of using this approach is that numeric identifiers are unique in the MIB tree, and they never change— human readable forms may be modified. 5) Search for and read RFCs and books on SNMP. For instance, a good book with more in-depth analysis of the MIB modules is “Understanding SNMP MIBs” by D. Perkins and E. McGinnis, et al. (published by Prentice

December 2002 · PHP Architect · www.phparch.com

Hall), while a good book for the SNMP protocol is “SNMPv1, SNMPv2c, SNMPv3 and RMON”, written by W. Stallings and published by Addison-Wesley. 6) Last but not least, don’t be frustrated if you don’t get everything working right away. Take your time and work through your problems one at a time.

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SNMP Management With PHP Figure 10: Protocol Functions SNMPv3

string snmpv3get ( string hostname, string username, string seclevel, string auth_protocol, string auth_passphrase, string priv_protocol, string priv_passphrase, string object_id [, int timeout [, int retries]]) array snmpv3realwalk ( string host, string username, string seclevel, string auth_protocol, string auth_passphrase, string priv_protocol, string priv_passphrase, string object_id [, int timeout [, int retries]]) bool snmpv3set ( string hostname, string username, string seclevel, string auth_protocol, string auth_passphrase, string priv_protocol, string priv_passphrase, string object_id, string type, mixed value [, int timeout [, int retries]]) array snmpv3walk ( string hostname, string username, string seclevel, string auth_protocol, string auth_passphrase, string priv_protocol, string priv_passphrase, string object_id [, int timeout [, int retries]]) array snmpv3walkoid ( string hostname, string username, string seclevel, string auth_protocol, string auth_passphrase, string priv_protocol, string priv_passphrase, string object_id [, int timeout [, int retries]])

Signing Off Now that we have briefly introduced SNMP its related PHP functionality, I think that it’s fair to say that PHP is a simple and rich language for creating SNMP scripts. Due to the wide variety of extensions available for PHP, such as those that allow for database and graphics functionality, the potential is there to write complex management applications that provide very advanced capabilities. In fact, there are already two SNMP opensource packages available at www.sourceforge.net— Figure 11 void snmp_set_enum_print(bool enum_print) void snmp_set_numeric_print(bool numeric_print)

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Harrie Hazewinkel is a long time participant in various open-source projects. He is the author of MOD-SNMP—an SNMP module with which the status of Apache can be monitored. He is an active participant in the Internet Engineering Task Force (IETF) and is the editor of the standard that defines managed objects for WWW services. His main expertise is Network Management and World Wide Web applications. Currently, he is an independent consultant and is open for new Internet challenges and adventures. You can reach him at [email protected].

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FEATURES

A Concrete Look at Database Abstraction Layers By Maxim Maletsky What is all this Database Abstraction fever? Why do we make so much noise about it and create so many different solutions, none of which seem to be able to make everyone happy? Perhaps, because not everyone tried to understand what the actual goal for abstracting database access is.

E

ver since PHP came on the market, proclaiming itself to be the world’s most beloved programming language, there has been a lot of disappointment over its weak cross-database portability. Indeed, for many developers, supporting pretty much all the existing databases through individual modules was simply not enough. Developers also want the possibility to avoid hardcoding db-specific functions in their applications— they want to call only one module (or object), tell it what DBMS to use and access their data transparently. As it turns out, that wasn’t a reasonable addition to PHP—simply because of its nature. First of all, PHP is not a true object-oriented language—it uses procedural functions to interact with DBMS systems, and libraries for different databases have to be called in different ways. Second, DBMS extensions are, internally, independent of each other—it would thus be almost impossible to synchronize them into one single object without first creating an OOP wrapper, which brings us back to the initial problem. PHPLIB As PHP evolved, PHPLIB came into existence. PHPLIB was a PHP library whose main goal was to allow for session management in PHP3. Session information was saved in a database and, with the intent of providing cross-database functionality, a transparent layer was used for data access. Not only you could save sessions into your favorite DBMS, but there was also a way for

December 2002 · PHP Architect · www.phparch.com

you to directly access these databases from your scripts, thus making PHPLIB the very first data abstraction layer available to PHP users. In PHPLIB, you’d call your database with something like this: This example would print an HTML table filled with 1 query("select * from employees"); 6 7 $t = new Table; 8 $t->heading = "on"; 9 $t->show_result($db); 10 ?>

results. Handy, isn’t it? Before you could get away with accessing your database using just five lines of code, however, you’d have to specify what DBMS should have been used via an included file. That was convenient for most cases—particularly for projects where the DBMS could have changed at some point in the future. If that “lucky event” were to happen to you, you’d simply have to REQUIREMENTS PHP Version: 4.0 and up O/S: Any Web server: Any Support Tools: A Database System supported by PHP

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edit the main PHPLIB configuration file to point to a new database configuration file. Besides sessions and DB functionality, PHPLIB also provided you with lots of other goodies, such as an authentication system, HTML rendering classes and much more. Unfortunately for PHPLIB (and luckily for all of us), PHP4 came out with sessions incorporated by default, making them simpler to use and allowing for the full cross-platform compatibility with no need to use any database at all that everybody was waiting for. When that happened, PHPLIB started becoming less and less popular—to the point that it was used just for its DB abstraction capabilities and, of course, the other “goodies” that people were so addicted to. Alas, even that didn’t last for too long... PEAR Soon after PHP4 was released, the PEAR project began. PEAR is a library similar to PHPLIB, with the allimportant exception that it was developed officially along the PHP core itself. It contains an extremely powerful set of database abstraction functionality—as well as many more useful tools. There are dozens of people who are working on PEAR today and thousands of people who use it. One of the main goals of PEAR is to provide PHP with a flexible database access system available on any platform (and for any DBMS). An example of database use with PEAR is shown in Figure 1. The PEAR DB class makes it quite easy to work with multiple databases. PEAR also allows you to use Data Objects so you can build very dynamic queries and connect several of the other available PEAR components to it. For instance, if you wanted to create a query which selects all the employees who are between 18 and 35 years old, with Data Objects you could dynamically build it this way:

1 whereAdd(‘age > 18’); 5 $employee->whereAdd(‘age < 35’); 6 $employee->find(); 7 8 while ($employee->fetch()) { 9 echo "{$employee->id} {$employee->name}
"; 10 } 11 ?>

This would compose and internally execute the following query:

SELECT * FROM employees WHERE age > 12 AND age < 30

December 2002 · PHP Architect · www.phparch.com

More DB Abstraction Modules Besides PHPLIB and PEAR, there are also a couple of other built-in extensions to PHP that allow for database abstraction, such as DBA and DBX. They are fast and flexible, but somewhat lacking in the compatibility department. There is also ADODB—a great and very powerful database library that is now available on a number of platforms. What the Ideal Database Abstraction Layer Should Do All these Database Abstraction Layers miss (at least) one thing. Sure, they do let you switch easily between all kinds of DBMS systems. The problem is that database systems do not simply differ in the way PHP interacts with them: they also often use a particular “dialect” of the SQL language that differs from the standard in subtle but significant ways. Thus, even though, theoretically, the word “Abstraction” between “Database” and “Layer” means you can accomplish the same task on any database server without editing a single line of your code, this is not entirely possible today because you will still have to modify your queries. For example, assume for a moment that we need to find out my age through SQL having only a string containing my birthday. In MySQL, the code will look like this: SELECT ( YEAR ( NOW() ) YEAR ( ‘1978-10-26 20:38:40’ ) ) as age;

In PostgreSQL, however, that will not work, and will have to be changed as follows:

SELECT ( EXTRACT( YEAR FROM TIMESTAMP ‘now’ ) EXTRACT( YEAR FROM TIMESTAMP ‘1978-10-26 20:38:40’ ) ) as age;

Oracle, on the other hand, requires quite a bit more work, as shown in Figure 2. All three SQL databases I used in the example claim to fully support SQL standards. The problem is, unfortunately, that the SQL standard is somewhat limited and not always adequate to the actual needs of every developer—as a result, you’ve just had quick proof that most DBMS systems do not (and, likely, never will) share the same SQL standard at all. Thus, if you’re used to having your SQL queries hardcoded in your applica-

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tion, you are going to have a very hard time rewriting most of them if you need to migrate it from one database to another. Ideally, a good Database Abstraction Layer should support differences in the SQL dialects for you. One way of doing this would be to dynamically rewrite the SQL code right within the db layer (such as ADODB does in some cases). However, as you can already imagine, this isn’t always a good solution, even if many DB layers try to implement it. For one thing, it’s not always possible to convert a SQL string written for a particular DBMS into its equivalent for a different DBMS in a univocal way; this means that it would be difficult (and dangerous) for the DB layer to “guess” what a SQL query means in every possible case. Another reason, and perhaps the most crucial one, is that parsing, “rethinking” and “repairing” every single SQL command would cause a significant performance hit that is not easily justified. The “good” database abstraction layers that we have today already slow things down enough—even without this feature. Finding a solution to this problem may look like an impossible dream. In reality, all it takes is a bit of foresight and some level of discipline. All you have to is to collect and save your SQL queries in a central location and use a sound dynamic mechanism to load them into

Theoretically, the word “Abstraction” between “Database” and “Layer” means you can accomplish the same task on any database server without editing a single line of your code. your code as needed. Consider the code in Listing 1—let’s call it mysql.sql.php—in which you hold your queries. As you can see, a separate variable is required for each SQL statement. Its value will later be injected into a call to a database, resulting in a system that can easily adapt to any DBMS—all you would have to do is to create another file, say postgresql.sql.php, that contains the SQL syntax appropriate for the DBMS you want to use. Of course, you will need a little framework that can use these files, providing you at the same time with the

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A Concrete Look at Database Abstraction Layers Listing 1: mysql.sql.php

1

ability to call the appropriate PHP functionality for the DBMS you choose to use. To put it simply, you need to come up with a simplified (but more powerful) version of what PHPLIB and PEAR do. Luckily, PHP supports Object-Oriented Programming (OOP) to a degree that is going to make this possible, and classes adapt very Figure 1 1 query($sql); 7 while ($row = $result->fetchRow()) { 8 echo $row[2] . '
'; 9 } 10 $db->disconnect(); 11 12 ?>

Figure 2 SELECT TO_CHAR ( TO_CHAR (sysdate,'YYYY') TO_CHAR ( TO_DATE ( '1978-10-26 20:38:40', 'YYYY MM DD HH24:MI:SS' ) , YYYY' ) ) "age"

well to this kind of requirement. There will be no actual queries passed to the class— we’ll pass a set of “aliases” (which we assign in mysql.sql.php) instead. This way, we will later be able to modify the SQL statements at will to adapt them to any DBMS from a single location. The first step consists of creating a “base” class that defines our fundamentals—the functions for connecting to a database, executing queries managing recordsets, and so on. This is shown in Listing 2, and provides us with a foundation of database-independent code to work on. Next, we need to create a specialized layer that sits atop the db_layer class to provide specialized database functionality. mysql_class.php (included in this month’s ZIP file), for example, shows a version of a db_layer subclass that provides the functions required to use MySQL. The mysql class implements those functions that the db_layer code calls whenever db-specific functionality is required. Under normal circumstances, a PHP script (such as the one in Listing 3) will need to instantiate our mysql class and then just call the “generic” functions defined by its db_layer superclass to access the database. Naturally, you can add more functions to the class (for example if you want to implement transactions), but you will always have to implement them using the same two-step approach, so that they can be adapted to other, different DBMS systems. A Look Under the Hood

FROM dual;

December 2002 · PHP Architect · www.phparch.com

Let’s now take a look at how the classes work. As you can notice within the code, most of the magic is per-

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Figure 3 1 connect('username', 'password', 'dbname', 6 'my.host.com'); 7 8 /* Pass alway same input values */ 9 $result = $db->query('age', 10 Array( 'date' => '1978-10-26 20:38:40' )); 11 12 /* And retrieve always same results */ 13 print_r($result); 14 ?>

formed by the db_layer class in response to the value of the $this->api_name variable, which it uses to determine where the SQL commands should be taken from (in our case, the mysql.sql.php include file). Each of the other db_layer functions are simply used as wrappers to the real database access calls that take place inside the appropriate subclass. What if you needed to change your DBMS? The first step would consist of creating another subclass of db_layer that implements the calls specific to your new database system. Next, you would need to create a new include file where all the queries are defined and, finally, you would need to change your PHP code so that it instantiates your new class rather than the old one. For this reason, I recommend that you instantiate

Listing 2 1 db_username = $user; 35 $this->db_password = $pass; 36 $this->db_database = $db; 37 $this->db_host = $host; 38 39 // Return positively on successful connection. 40 Return $this->api_connect(); 41 } 42 43 44 /* Method: query 45 +------------------------------------------------------------------+ 46 Description: Execute Query 47 +------------------------------------------------------------------+ 48 */ 49 50 function query($alias = '', $data = '') { 1

Continued On Page 40...

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FEATURES the database class in a global include file—so that you would only need to change it in one place should you ever need to switch DBMS. A Few Closing Notes As you can imagine, it’s easy to come up with a number of possible extensions to the code I presented in this article. One possibility is the use of transactions, as I mentioned above. Another one could be the addition of some specialized form of error handling, which would give you the opportunity to trap errors and provide “sanitized” notification messages to your users. Similarly, you could create specific configuration instructions for every DBMS right within their respective SQL files. This could be handy when one database has to do something that others can’t or don’t need to. For instance, I used this method in a situation in which a single Oracle query was worth three of MySQL’s, and yet I needed to make a single call and obtain the same result set. To update two tables with Oracle, I used a PL/SQL code block or a stored procedure, both unavailable in mySQL. This would make a single codebase impossible, since in one case you’d have to execute a single command, while in the other several SQL statements have to be run. If you were to modify your abstraction class so that multiple queries can be specified with a single alias, your call would still look like the code in figure 3. Handling Database Abstraction this way gives you infinite possibilities (as well as infinite possibility to

needlessly complicate things). The trick is in only using this approach if you think that there will be a reasonable need in the future to move your current applications to a different DBMS. However, Database Abstraction can be a very powerful tool, particularly if you’re writing applications that will be used by different people in different environments, as it is often the case with open-source projects. Think how complicated would be to write a forum application and then distribute it over the world without having a well-structured DB abstraction layer! To see a more complex, yet fully working example of Database Abstraction logic similar to the one I used in this article, take a look at the ZoomStats project on S o u r c e F o r g e (http://www.sourceforge.net/projects/zoomstats). It was born as a web traffic analyzer, but is slowly becoming a whole OOP Database Abstraction Layer of its own! Also, both PHPLIB and PEAR are very much alive and kicking; you can find the former at http://phplib.sourceforge.net and the latter at http://pear.php.net. php|a

Maxim Maletsky is an IT Consultant currently taking care of the e-government infrastructures in Italy. Maxim’s spare time and sleep are almost completely wasted on hassling with the official Oracle extension for PHP, bug hunting, phpnotes moderation, answering all kinds of posts on PHP mailing lists and writing. You can get in touch with him at [email protected].

Listing 3 1 connect('username', 'password', 'dbname', 'my.host.com'); 16 17 /* Here you will execute the query and get 18 * the result set returned as array 19 */ 20 21 $result = $db->query('age', Array('date' => '1978-10-26 20:38:40')); 22 23 print_r($result); 24 25 /* This should print you: 26 * Array 27 * ( 28 * [age] => 24 29 * ) 30 */ 31 ?>

December 2002 · PHP Architect · www.phparch.com

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Listing 2: Continued From Page 38... 51 52 // Connect to API 53 $this->connect(); 54 55 // Store Alias 56 $this->db_alias = $alias; 57 $this->db_data = $data; 58 59 extract($this->db_data); 60 61 // Include SQL storage files 62 @include($this->api_name . '.sql.php'); 63 64 // Check existence of query 65 $this->db_query = isset($query)? $query : die('No query for alias ' . $this>db_alias); 66 67 // Clean trailing semicolons ';' in SQL 68 $this->db_query['sql'] = isset($this>db_query['sql'])? preg_replace("/;?\s*$/s", '', $this->db_query['sql']) : ''; 69 70 // Execute Query 71 $this->api_execute(); 72 73 // Return result: 74 Return $this->result(); 75 } 76 77 78 /* Method: result 79 +------------------------------------------------------------------+ 80 Description: Return results. 81 +------------------------------------------------------------------+ 82 */ 83 84 function result() { 85 86 // Number of Rows 87 $this->db_rows = $this->api_rows(); 88 89 // Number of Columns 90 $this->db_cols = $this->api_cols(); 91 92 // Compose array 93 $r = 0; 94 while($r<$this->db_rows and $this->api_next_record($r)) { 95 96 // Loop values 97 foreach($this->db_record as $col=>$val) { 98 $this->db_result[$r][$col] = $val; 99 } 100 101 // increment row count 102 $r++; 103 } 104 105 // Return Results 106 Return $this->db_result; 107 } 108 109 /* Method: close 110 +------------------------------------------------------------------+ 111 Description: Close Database Connection 112 +------------------------------------------------------------------+ 113 */ 114 115 function close() { 116 117 // Close database connection 118 $this->api_close(); 119 Return True;

December 2002 · PHP Architect · www.phparch.com

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Creating A Multi-iitem Visual Catalogue System With PHP & Internet Explorer By Davor Pleskina Many web-based “Catalogue Systems” have cropped up on the Internet scene lately, either as online stores or advanced ordering systems of some kind (such as subscription systems). The catchwords that are usually employed to describe them include “interactive” and “visual”—which usually means simply that users (or, should we say, potential clients) visiting them should be able to review the products offered for sale through sets of images, add them to a virtual shopping basket through a single mouse click and, finally, let the system process their order.

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learly, this entire process should be as seamless as possible: users don’t need to know how the system works, and any hiccups can cause the store owner to lose a customer. A Look at How a Catalogue System Works

As with many computer-related technologies, there is no real “standard” way of developing a “visual” catalogue system. However, most of the existing implementations seem to have focused on either showing pic-

We will always run the same script, but it will behave in a different way, depending on the parameters that are passed to it. tures of individual products, or showing pictures in which more than one product is displayed (as it is often the case, for example, with stores that sell spare parts). In that case, each of the products in the picture can be clicked on individually.

December 2002 · PHP Architect · www.phparch.com

Whenever confronting the need to develop a new catalogue system, developers tend to get lost in technology—names like Macromedia Flash and Java start to float around and, pretty soon, a simple idea becomes a complex monster. In reality, it is possible to develop a very powerful catalogue system using mostly serverside functionality, with just a little help on the client side. In this article, I present a simple and yet powerful “visual” catalogue system, based on PHP and MySQL for server-side functionality, and nothing more than a lot of IE HTML and some Javascript on the client side. The great thing about a system like the one I will show here is that it requires very little in the way of functionality as far as the browser is concerned. This, in turn, means that there won’t be a need for any plug-ins or other downloads and that your application will be compatible with a great majority of the client systems out there. Best of all, our entire catalogue system will require just one file in the frontend—thus providing a compact profile that can be optimized to maximum extent possible.

REQUIREMENTS PHP Version: PHP 4 with Sessions enabled O/S: Any Web server: Any Support Tools: MySQL

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Scope of The Application Our system will support the following functionality: · Catalogue Selection · Article Selection · Basket Preview Naturally, a complete on-line catalogue system would normally support more functions than what we have here, but they would be outside the scope of this article. These include basket editing, order processing, Figure 1

handling more than one product set, and so forth. Most of these functions are just a small step away from the ones we will look at here and can be easily added through techniques similar to the ones that I have used. Our sample application will only provide two “catalogues”, each represented by a single JPEG image that contains a variable number of products. Users will be first asked to select a catalogue, and then a product by clicking on it in the image. Finally, they can specify a number of items for that product and add them to their shopping basket. At any time, users can also switch to a different catalogue or review their baskets (unless, of course, the application has just started, in which case a catalogue must be selected before any other action can be undertaken). Figure 1 shows the system’s workflow diagram. In “Catalogue Selection” mode, each catalogue is presented as a link that can be clicked to show the products it contains. When a user clicks on a catalogue, December 2002 · PHP Architect · www.phparch.com

the system immediately goes into “Article Selection” mode, showing the catalogue’s image with clickable areas for each of the products. Moving the cursor over these areas displays a simple “tooltip” containing information about the appropriate product. Once the user clicks on one of the areas, the system shows an input form with a “Quantity” field and an “Add” button for the selected product. Pressing the Add button stores the product and quantity information into the basket and displays a confirmation message, returning at the same time to Article Selection mode. The system also features a “Basket Preview” mode, which shows the basket’s contents. Sounds simple? Well, the process is really not that complicated at all—it would have to be that way, since the goal of the application is to make it as easy as possible for the user to make a purchase. To make everything work in a smooth and optimized way, however, we’ll have to dig a few tricks out of our good old PHP hat. So, How Are We Going To Do That? Let’s take a look at some of the techniques that we’ll use to develop our visual catalogue. First of all, since it’s “visual”, we’ll need a few pictures—I’ve added a couple of them in the images/ folder of the project (you should find all the code in the ZIP file that you received when php|a was delivered to you). We’ll be selling two types of products (and, therefore, we’ll use two catalogues): fruits and kitchen accessories. Next, we’ll need someplace to store the information about our catalogue and, since we’ve mentioned the use of MySQL, we’ll store all our data in Figure 2 a set of nicely defined tables (shown in Figure 2). You’ll notice that, because we use a single image for each catalogue, we’ll also have to describe the areas that correspond to each product in the catalogue. This is done in the CATAREA table, which also links articles to catalogues. Naturally, our tables need to be filled with some data, which you can see in Figure 3. The CATAREA table is used as a “bridge” between CATALOGUE and ARTICLE, so that each article can be assigned to the proper catalogue. In addition, the POINTS column is also used to specify the bounding areas that define the position of each article in its

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Table “CATALOGUE”: CAT_ID DESCRIPTION ——— ————————————————————1 Fruit and Vegetables 2 Accessories

IMAGE_NAME ———————————— cat1.jpg cat2.jpg

Table “ARTICLE”: ARTICLE_ID ————— APPLE PAPRIKA LEMON ONION MANDARINE SUGARPOT PLANT

ARTICLE_NAME —————————Apple Green paprika Fresh lemon Onion Mandarine Sugar pot Plant in the glass

HONEY

Honey with dry fruit

DESCRIPTION —————————————————This is tasty and very sweet apple! Have you ever tried fried paprika? Make yourself a lemonade! Excellent salad add-on! Enjoy this sweet fruit Use it while drinking coffee Decorate your working space with this plant Delicatessen

PRICE ——5.00 3.20 4.00 2.10 3.50 11.45 16.00 20.00

Table “CATAREA”: CAT_ID ————1

AREA_ID ———1

ARTICLE_ID ———— APPLE

1

2

LEMON

1

3

MANDARINE

1

4

ONION

1

5

PAPRIKA

2

1

SUGARPOT

2

2

PLANT

2

3

HONEY

POINTS —————————————————————— 421,321,463,265,536,254,594,279,636,353, 611,425,524,454,470,436,420,375 57,192,68,120,147,69,226,95,215,165,146,216, 77,220 15,315,40,266,99,245,150,255,191,311, 178,363,156,392,104,411,51,398,28,362 433,181,456,138,486,123,479,39,532,39, 525,113,568,143,595,196,572,238,515,255, 478,260,442,215 238,327,240,136,308,103,382,129,401,192, 398,248,356,356,333,379,298,392,272,383 121,125,187,198,228,287,215,334,158,366, 98,351,70,301,86,244,82,195,98,138 182,178,217,90,434,89,481,184,407,216, 385,272,330,292,271,267,253,214 457,206,533,193,591,225,595,284,567,353, 492,391,452,372,425,298

respective catalogue image. These, in turn, will be used later on by our PHP script to create an HTML MAP element so that the user can actually click on the articles and produce the desired result. Another important technique we are going to use is sometimes referred to as “Parametrized Script Navigation”. Fancy words aside, this simply means that we will always run the same script, but that it will behave in a different way, depending on the parameters that are passed to it when the browser is requesting a page. The advantage of this method is that all your code is contained in a very limited number of files (only one in our case!), and that promotes reusability. The disadvantage is that it’s easy to let things get out of hand and end up with a bowl of spaghetti. With a bit of care, however, this problem can be easily taken care of. We will call our navigational parameters “Mode” and

December 2002 · PHP Architect · www.phparch.com

“Action”. The former will represent the application’s current state (such as “Catalogue Selection”), while the latter will indicate what action should be taken under current Mode. I’m sure that some of you might be wondering, at this point, whether the two parameters could have been incorporated in a single GET variable. In this case, I felt that two separate parameters would make extending the application much easier in the future. Since the catalogue system that we’re looking at here is rather simple and must be expanded upon to build a complete application, I think that a modular design approach brings many benefits. On To The Code The first things that we are going to need in our script are some variables whose life spans beyond the

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script’s execution. These variables should be registered within a session. Sessions are PHP’s way to preserve certain data across subsequent calls to scripts on a web server or in a web server farm. Sessions start from the first access to the script and last until either they are explicitly destroyed or after a pre-defined period of inactivity. Session state is maintained either through a cookie or by appending a specific parameter to the script’s URL. We’ll use the former method, since it’s generally more discrete and convenient. A session should be started by calling the session_start() function before any contents (including blank lines) are outputted to the client. This is because the server must write a cookie to the browser, and this is done through the page headers. If your copy of PHP has output buffering turned on, this is not necessary, but you should adopt this methodology as a rule to maximize the portability of your code. Our session initialization code is shown in Listing 1. Looking closely, you will notice that we assign values to three variables, $mode, $action and $cat_id, which Figure 4

Change Catalogue    Select Articles    View Basket   

These links never change and are always shown to the user (you can see them at the top of Figure 4). As you can see, each link redirects to the viscat.php script itself, and that the two parameters p_mode and p_action are passed to it. When the users click on any of these links, their browser will reopen the script but with different parameters, allowing our script to decide which code blocks to execute. Listing 2 shows how these parameters are used in our code. If no value is assigned to them, the script is probably being executed for the first time and $mode and $action will be set to “1” (Catalogue Selection) and “0” (Default Action) respectively. If at this point, for any reason (such as potentially malicious usage of the script), $cat_id is less than 1 we print out an error and force the user to choose a new catalogue before continuing: if (($mode > 1) && ($cat_id < 1)) {

respectively contain the current mode, the action to be performed and the ID of the catalogue currently selected. They are assigned different names from their URL parameter equivalents for a very specific reason. If you were to enable the register_globals functionality in your copy of PHP (it has been disabled by default since PHP 4.2), having your internal variables and the URL parameters share the same name could lead to severe security issues, since a malicious user would be able to manipulate the values internally used by your scripts. After we have processed our initial tasks and prepared our script for web page generation, it’s time to output a few links that will go in our header:

print “Please select a catalogue first!
”; $mode = 1; }

This way, we can we can avoid logical errors by ensuring that a catalogue has been chosen before undertaking any other actions. Enter the Database After this initial parameter checking, we must connect to our MySQL database in order to allow the rest

Listing 1 1 10

December 2002 · PHP Architect · www.phparch.com

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FEATURES Listing 2 1 "; 13 print "MySQL Error " . mysql_errno() . ": " . mysql_error() . "
"; 14 print "Exiting..."; 15 // We leave... 16 exit; 17 } 18 19 } 20 21 22 ?>

of the script access to our dynamic catalogue data (Listing 3). The variable $mycon_id will be set to a valid MySQL resource in case of a successful connection. Otherwise, the script will output an error and stop its execution. In my example code, I assume that the database the application relies on is called “davor”, and can be accessed by the user “root” with no password. Naturally, in your own experiments you are free to use your own settings—just remember to change them in the source code. The last thing to do in this part of the code is to display the appropriate information about the active catalogue. If a catalogue was previously selected, the $cat_id variable must be set to a value greater than 0. The code in Listing 4 will extract its name from the CATALOGUE table and show it at the very beginning of our HTML table. We also store the name of the catalogue’s image in the $image_name variable.

Case In Point We have now reached the decisional part of our script, shown in Listing 5. The script uses the “switch” control structure to check the value of $mode and branch the script’s execution to specific functions designed to handle each of the three application modes. As a special case, let’s now take a look at what happens when the script is accessed for the first time. The $mode variable will be set to 1, thus forcing the system into catalogue selection mode. The function CatalogueProcedures() will be called, resulting in the display of the catalogue selection page. Clicking on any link except “Change Catalogue” in this state will result in the message “Please select a catalogue first!” being displayed and no further action being taken.

Listing 3 1

From here on, we will generate HTML code using PHP --> Let's connect to our database - we will use $mycon_id variable; If a connection has already been established, $mycon_id will be other than NULL... (!$mycon_id) $mycon_id = mysql_connect("localhost", "pleskina_public", "viscat"); if ( (!$mycon_id) || (!mysql_select_db("pleskina_viscat", $mycon_id)) ) { // Let's inform about the error and get out print "Could not connect to the database!
"; print "MySQL Error " . mysql_errno() . ": " . mysql_error() . "
"; print "Exiting..."; // We leave... exit; }

December 2002 · PHP Architect · www.phparch.com

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Visual Catalogue System With PHP & IE Listing 4

1 0) 4 { 5 $data_row = mysql_fetch_array( 6 mysql_query( "SELECT * FROM CATALOGUE WHERE CAT_ID='" 7 . mysql_escape_string($_SESSION['cat_id']) . "'", $mycon_id) 8 ); 9 $image_name = $data_row["IMAGE_NAME"]; 10 print "<EM>Active catalogue is: " . $data_row["DESCRIPTION"] . "
\n"; 11 } 12 13 ?>

Choosing an Article: The Real Fun Begins So far, things have been quite simple—but they’re about to get complicated. In Article Selection mode, we must show the appropriate catalogue image and generate the image areas to allow the user to click on the item he or she is interested in. Let’s look at the code in Listing 6, which shows the source for the ArticleProcedures() function. Here, we have two possible actions, but we use a little trick because one of them (action 0) is really a portion of the other. While going through the case statement, the action zero commands will be performed even when $action is set to 1, thanks to the fact that the case 1 block does not end with a break; statement. Although it can seem illogical at first look, coding action 1 first is quite reasonable—this action means that some article was passed to the script and that it

should be added to the basket. Even if that is the case, we still have to provide the user with an opportunity to view and choose the other articles—and that is the duty of the case 0 code block. This works by outputting a <MAP> HTML code block called #imagemap, which is defined in the usemap parameter of the image tag for the current catalogue. The map contains the coordinates of selectable (clickable) polygons that define the shapes of each article on our catalogue image. Each AREA tag is represents a polygon whose coordinates are relative to the catalogue image and are retrieved from the CATAREA table. The alt tag provides name, price and description information that is displayed when the user moves the cursor over the polygon. A little Javascript magic allows us to transfer some of the catalogue’s functionality directly to the client. The onClick event added to each AREA tag passes two parameters, a text string and the value of ARTICLE_ID,

Listing 5 1 Catalogue Selection:

---

"; 10 // Now invoke procedures used to select catalogue etc. 11 CatalogueProcedures(); 12 break; 13 } 14 case 2: // Selecting Articles 15 { 16 print "Selecting Articles
"; 17 // Call procedures handling article selection 18 ArticleProcedures(); 19 break; 20 } 21 case 3: // Selecting Articles 22 { 23 print "Basket Preview
"; 24 // Go to function which handles basket contents 25 BasketProcedures(); 26 break; 27 } 28 } 29 30 ?>

December 2002 · PHP Architect · www.phparch.com

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to the script that is dynamically generated in lines that follow. The ShowArticleInfo() Javascript function changes HTML content of a

element named “artinfo” so that it contains a

for entering a quantity and adding an article to the basket. Every AREA’s onClick event code passes its own description and ARTICLE_ID to ShowArticleInfo(), so that when the user clicks on a particular area, the appropriate information is shown at the bottom of the screen. Clicking the “Add” button passes the ARTICLE_ID with the appropriate “mode” and “action” parameters to our script again in order to add the article to the basket. This approach simplifies our PHP code somewhat, since we don’t have to handle article selection through a series of back-and-forth calls to our script. However, it does come at a price, since making an HTML page that

As with many computer-related technologies, there is no real “standard” way of developing a “visual” catalogue system. relies so heavily on Javascript on all browsers can be a challenge that might not be worth its rewards.

The last mode of our application (number 3) provides the necessarily functionality to view the user’s baskets. The BasketProcedures() function outputs the contents of the basket session variable contents by formatting htem in a table. Where To Go From Here While the visual catalogue that I have presented in this article provides a number of unique techniques that can often be useful in any type of project, there is still a very long way to go before this application can be used in a production environment. First of all, the entire e-commerce portion—the one where the users pay you—is missing. Still, there are many e-commerce packages out there, and the truly unique idea that I wanted to provide you with was the catalogue itself. Security and access control can certainly be examined and audited ad nauseam, and they, too, would be part of a more complete solution that could be deployed in a real-life scenario. So, in closing, I wish all of you good luck with the development of your catalogue systems—hopefully, I have been able to show you that building one is not really that tough.

php|a

Davor Pleskina lives in Opatijia, Croatia. He is the author of Davor's PHP Editor, which we review in this issue of php|a. You can reach Davor at [email protected].

Listing 6 1
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Visual Catalogue System With PHP & IE Listing 6: Continued From Page 47...

27 if ($data_row) 28 { 29 $basket_row = array( $p_article_id, 30 $data_row["ARTICLE_NAME"], 31 (int) $p_quantity, 32 $data_row["PRICE"], 33 $p_quantity * $data_row["PRICE"] ); 34 $_SESSION['basket'][] = $basket_row; 35 36 print "{$_REQUEST['p_quantity']} pc(s) of Article '{$_REQUEST['p_article_id']}' " 37 ."has been added to your basket.
\n"; 38 } 39 } 40 41 case 0: // Display image and load areas 42 { 43 // Display image from physical file 44 print "\n"; 45 // Load and display areas 46 $data = mysql_query( "SELECT * FROM CATAREA, ARTICLE ". 47 "WHERE ARTICLE.ARTICLE_ID = CATAREA.ARTICLE_ID ". 48 " AND CAT_ID='" . mysql_escape_string ($_SESSION['cat_id']) . "'", 49 $mycon_id); 50 // Create a map 51 print "<MAP name='imagemap'>\n"; 52 while ($data_row = mysql_fetch_array($data)) 53 { 54 print "\n"; 61 }; 62 print "\n\n"; 63 // Next

is used to display article info and input form 64 print "

"; 65 // Following script is creating appropriate form depending on article selected 66 print "<script language='JavaScript'> \n"; 67 print " function ShowArticleInfo(info, article_id) \n"; 68 print " { \n"; 69 print " window.artinfo.innerHTML = \n"; 70 print " ''+ \n"; 72 print " ' '+ \n"; 73 print " ' pcs'+ \n"; 74 print " ' '+ \n"; 75 print " ' '+ \n"; 76 print " ' '+ \n"; 77 print " ' of  '+info+', to your basket'+ \n"; 78 print " ''; \n"; 79 print " document.forms[0].elements[1].focus(); \n"; 80 print " document.forms[0].elements[1].select(); \n"; 81 print " } \n"; 82 print "\n \n"; 83 break; 84 } 85 86 } 87 88 }; 89 90 ?>

December 2002 · PHP Architect · www.phparch.com

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Writing a Web-b based PDF Converter By Marco Tabini Ever wondered whether an alternative to those expensive client-based PDF converters for Windows existed? Well, look no further: with a few open-source applications a handful of lines of PHP code you can write your very own web-based converter and save big bucks!

E

ver since their inception, Portable Document Format (PDF) files have become the medium of choice for transmitting typographically accurate files over the Internet (even php|a uses them!). Regardless of whether PDF technology truly represents the best medium for transmitting files online, Adobe’s timeliness in releasing it to the market, as well as the fact that PDF readers are widely available for most platforms, have contributed to its popularity. For many Windows users, however, producing PDF documents is a less than pleasant endeavour—mostly because pretty much all the conversion software currently available is commercial in nature and, therefore, carries a license fee. Linux users are in a better situation, considering that their printing subsystems are largely based on PostScript and that most Linux distributions include a copy of Ghostscript, an open source PostScript interpreter that is natively capable of writing PDF files. Still, even on Linux creating a PDF file can be a multi-step process that often involves shell operations beyond the average user’s abilities. A Zero-cost Alternative If people in your organization need to create PDF files, the simple PHP solution that I present in this article can save you a significant amount of money without in any way degrading the user experience that you and your colleagues would expect from a commercial application. Because my solution can be entirely based

December 2002 · PHP Architect · www.phparch.com

on open-source software, there are no costs associated with it (other than, perhaps, setting up a new server once your colleagues, freed from the bond of commercial-software dependence, will give in to the temptation of converting all their documents to PDF). The concept behind my PDF converter is rather simple: create a website that allows someone to post a file and receive it back converted to PDF. The trick here is to ensure that the files passed to the system are always in PostScript format, regardless of what application generated them. This can be accomplished by installing a PostScript printer driver on the client machine and then “filter” the source files through it by printing them on a fictitious PostScript printer that saves its output to a file. Luckily, this is much easier to do than it sounds. Linux, as I mentioned above, supports PostScript as pretty much it sole print spooling technology. As such, all you need to do to convert your files to PostScript format is to print them as you would normally do but, instead of piping your output to a printer, save the resulting PostScript code as a file. Under Windows, the installation is a bit more complex—but still mostly trouble-free even for a relatively REQUIREMENTS PHP Version: 4.0 and up O/S: Any Web server: Any Support Tools: Ghostscript 5.0 and up

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FEATURES unsophisticated user. The first step is to find a printer driver that is suitable for your version of Windows. If you’re running any version of Windows NT, Windows 2000 or Windows XP, a PostScript printer driver comes bundled with your operating system. This driver is actually quite good and, if properly configured, will give you excellent results. If you’re running Windows 9x or Windows ME, you can download a PostScript driver for free from the Adobe website. Installing the PostScript Driver Under Windows NT/2000/XP To install the PostScript Driver, go to your Start Menu, then choose Settings and, finally, Printers. This will pop up your printer folder, where you can click on the Add Printer icon. At this point, all you have to do is follow the Add Printer wizard, keeping in mind that: · You want to create a local printer that points to the “FILE:” port. This will force the print spooler to prompt you to save the PostScript output to a file rather than redirect it to a real printer · The printer driver for your printer is called APSPS PIP with APS-6-108 v.49.3 or 52.2 (a clear indication that Microsoft and Adobe need to come up with shorter acronyms) and its “manufacturer” is APS-PS. Once you have installed the printer driver, there is one important configuration step that you have to undertake that will dramatically increase the quality of your PDF files. Right-click on your newly created printer from the Printers folder and choose Properties. In the Device Settings tab, ensure that both the Minimum Font Size to Download as Outline and Maximum Font Size to Download as Bitmap parameters are set to 1. This is necessary because most of your applications will try to send text data to the printer based on TrueType fonts. Because PostScript does not natively support TrueType, the printer driver will try to convert them to some other PostScript-compatible format for you. Under normal circumstances, for legibility reasons, fonts of sizes below the value of the Minimum Font Size to Download as Outline above are downloaded as Type3 PostScript font bitmaps. This results in an extremely poor on-screen quality for your PDF files, since the PDF renderer does not have enough information about your fonts—after all, they are now nothing more than mere bitmaps as far as it is concerned—to produce high-quality output at your screen resolution. On top of this, your PDF files will also be larger, since fonts are downloaded as bitmaps rather than in vector format. By manipulating the driver settings as described above, you’re essentially forcing the driver to download December 2002 · PHP Architect · www.phparch.com

Writing a Web-Based PDF Converter all fonts as outlines—that is, as vector graphics—which, in turn, give the PDF renderer an opportunity to produce a pleasant and professional-looking output at all resolutions.

The concept behind my PDF converter is simple: create a website that allows someone to post a file and receive it back converted to PDF Windows 9x/ME Setup Since older versions of Windows (with the exception of Windows NT, which we covered in the previous section) do not have a built-in printer PostScript printer driver, you will have to download one—free of charge—from Adobe at the following URL: http://www.adobe.com/support/downloads/product.jsp ?product=44&platform=Windows Before installing the driver, however, you will need a PostScript Printer Description (PPD) file. PPD files are used by the PostScript driver to find out about the capabilities of a specific printer. Since in our case there is no real printer, all we need to do is find a PPD that closely matches the capabilities of a PDF file. Adobe supplies a generic PPD file (built into the driver) that works just fine, with the exception that it converts all graphics to greyscale. However, you can easily find other PPD files at many locations, such as the Linux Printing website (http://www.linuxprinting.com), which, despite its name, contains a treasure chest of printer definition files that can easily be used with the Adobe driver. The only problem with the installation of this driver is that you have to decide which PPD file to use during the setup process, since you cannot change it later. Once you have installed and downloaded the driver, it must be configured in pretty much the same way as its Windows 2000 counterpart, only this time the settings are in the Fonts tab of the printer properties dialogue box. Ensure that Substitute printer fonts for TrueType fonts when applicable is deselected, then click on the Send Fonts As… button, choose “Outlines” From the Send TrueType fonts as… drop-down box and, finally, ensure that the threshold to switch between bitmap and outlines is set to one, so that the printer driver is forced to create high-quality fonts as part of the PostScript output.

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Creating PostScript Files Whenever you now want to create a PostScript rendering of any of your documents, all you will have to do is open the appropriate application, load the file and print it to the dummy PostScript printer that you have created. The operating system (or, in some cases, the application itself) should prompt you to choose a name for your PostScript file and generate it for you. This system provides a very general method of creating PostScript files and, in my experience, works well with pretty much any application—from web browsers to professional publishing applications. It’s the approach that we use to create your personalized copy of php|a—and the results are, as you can see, quite good (allow us a bit of pride!).

code needed for the browser’s upload functionality. The second provides all the processing and outputs the converted PDF file. Naturally, it would be possible to easily combine the two files in a single script—I am keeping them separate for the sake of clarity. In order to be able to run this application, your server must be able to accept file uploads. This can only be accomplished if your copy of PHP was compiled with the file upload capabilities and if those capabilities are turned on. Because PostScript files can get quite large, it’s also important that you ensure that your file upload settings allow files of at least 20MB to be uploaded. This may seem like a lot, but it’s not too difficult to exceed that size when you’re creating a PostScript file that contains lots of graphics. Figure 1 explains a simple procedure that you can use to enable file uploads. Preparing the File Upload

The PHP Application Now for the second half of our mission to create a web-based PDF converter. The next step consists of developing a simple web site that allows the user to upload a file and then convert it to PDF using Ghostscript. The solution that I will examine uses two separate PHP files, index.php and postps.php. The first file acts as a gateway into the system and provides the HTML

The file index.php, whose contents you can see in Listing 1, is the starting point of our application. As you can see, there actually is no PHP code in this file, although in a real-life example you may want to provide some sort of authentication, to ensure that your PDF converter is not abused by unauthorized users. As you may have noticed, the submission form includes the enctype parameter, which is set to a value of multipart/form-data. This is necessary so that the

Listing 1: index.php 1 15 16 17 18

PDF Distiller

19 Please upload your PostScript file here. 20

21 22 23 26 29 30

24 Please choose a file 25

27 28

31

32

33 34 35

December 2002 · PHP Architect · www.phparch.com

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Writing a Web-Based PDF Converter Listing 2: postps.php

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 ],


PDF Distiller By Marco Tabini From the December, 2002 Issue of php|architect Copyright (c) Marco Tabini and Associates, Inc.

// Turn on error reporting error_reporting (E_ALL); // Creates a simple HTML page with a message and aborts the script // We use this function for reporting errors to the user function print_message ($s) { die (‘

Warning!

’ . $s . ’’); } // Check that a file was uploaded

if (!count ($_FILES) || $_FILES[‘infile’][‘error’] || strcmp ($_FILES[‘infile’][‘type’ ’application/ postscript’)) 29 print_message (‘No file uploaded or upload error!’); 30 31 // Try running it through Ghostscript 32 33 exec (‘gs -sDEVICE=pdfwrite -r300 -sOutputFile=’ . $_FILES[‘infile’][‘tmp_name’] . ’.pdf -dNOPAUSE -dBATCH‘ . $_FILES[‘infile’][‘tmp_name’], $a, $n); 34 35 if ($n) 36 print_message (‘Unable to convert file. Please ensure that you have used the proper format and try again.’); 37 38 // First, output headers that tell the browser the type of the file 39 // we’re outputting, how long it is and how we want it displayed 40 // The Content-Disposition header also allows us to specify a filename 41 42 header (‘Content-Type: application/pdf’); 43 header (‘Content-Disposition: attachment; filename=”’ . $_FILES[‘infile’][‘name’] . ’.pdf”’); 44 header (‘Content-Length: ‘ . filesize ($_FILES[‘infile’][‘tmp_name’] . ’.pdf’)); 45 46 // Dump the PDF file and delete it from the PHP folder 47 readfile ($_FILES[‘infile’][‘tmp_name’] . ’.pdf’); 48 unlink ($_FILES[‘infile’][‘tmp_name’] . ’.pdf’); 49 ?>

browser will format the POST parameters of its HTTP query to the server utilizing the “multi-part” standard, which essentially enables for the POST data to be split in separate units (or “parts”), each representing a single entity—a file in our case. Omitting this parameter will prevent your file upload from working, and is normally a substantial source of frustration for the beginner (at least, it was for this beginner when he started out). The worst part is that, if the enctype parameter is not specified, the browser still uploads the file, so that the whole operation seems to take place in a normal

December 2002 · PHP Architect · www.phparch.com

fashion—except, of course, that it doesn’t work. Another thing that you may notice is that I have not bothered to specify a maximum file size in the HTML code. This is normally done by including a hidden form field called MAX_FILE_SIZE, whose value represents the maximum size, in bytes, of the biggest file that the browser should accept to upload. There are two reasons for my choice: first, this is intended to be an Intranet application, so that you should not be particularly concerned about bandwidth usage. Second, most browsers seem to ignore this setting anyway, so that it

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Writing a Web-Based PDF Converter Figure 1: Enabling file uploads

In order to enable file uploads, you should have access to your php.ini file. To find out where this file is located, write and execute a simple one-line PHP script;

The resulting output will provide you with a wealth of information—including the location of php.ini. Inside the file, look for the following items: file_uploads Indicates whether file uploads are allowed (“On”) or disallowed (“Off”). upload_max_filesize Indicates the maximum allowed upload size. You can actually use “human-readable”

values here. For example, 20M means 20 megabytes. If you’re using Apache, another way to configure file upload capabilities consists of changing your web server’s configuration file. In this case, you can set the values of file_uploads and upload_max_filesize using the php_admin_value and php_admin_flag Apache configuration keywords. In this case, you can even enable file uploads on a per-virtual-server basis: php_admin_flag php_admin_value

file_uploads upload_max_filesize

really does not make a big difference to have it or not— the real checks are performed on the server side. Processing the File Once the user has chosen to upload a file, this will be passed to postps.php (assuming, of course, that it hasn’t been blocked by PHP itself because it exceeds the maximum allowable file size), which you can see in Listing 2. The first thing that this script does is to verify that a file was, indeed, uploaded and that the server recognized it as a PostScript file. Keep in mind that this is not an omni-comprehensive test—it is, in fact, quite easy to send a fake PostScript file and cause the server to recognize it as such. The goal, at this stage, is to ensure that something was at least sent to the script and to perform a cursory examination to prevent the most obviously wrong cases from going forward. Next, on line 33 the script calls Ghostscript to convert the file. As you can see, the call passes several switches to the Ghostscript application; they are explained in Figure 2. You have also probably noticed that the script simply reuses the temporary filename that was assigned to the PostScript file when it was uploaded, with a .PDF extension appended to it. This is a simple trick that ensures that the generated file will still be unique— although it also causes the script to create a new file in the folder that you have reserved for file uploads. If Ghostscript returns an error, the script aborts by telling the user that it is unable to convert the file. This step is necessary because, as I mentioned above, the script cannot be sure that all the files that pass the initial tests are, in fact, valid PostScript files (after all, that’s Ghostscript’s job). Lines 42 through 44 output a set of headers that provide the browser with some important information December 2002 · PHP Architect · www.phparch.com

On “20M”

about the file we’re about to send. The first, ContentType, indicates that the MIME type of the file the script is about to output is application/pdf (which identifies a PDF file). Content-Disposition, on the other hand, indicates that the file should be treated as an attachment (that is, that it should be treated as an external file and not displayed within the browser’s window), while at the same time also providing a new filename that the browser will use instead of the name of our PHP script. Finally, Content-Length tells the browser how big the file is. This can be used by the browser for several purposes, including determining whether the file can be downloaded and saved to the user’s hard disk. Finally, the file is outputted to the browser using the readfile() function, and deleted with unlink(). This last step is very important, since if you do not delete your the files you create they will remain in the filesystem and may, eventually, cause disk space issues. Almost There, But Not Quite At this point, if you’re using Internet Explorer and Adobe Acrobat Reader to display your PDF files, you will notice that something rather odd happens when you successfully convert a PostScript file into PDF. The browser’s “File Download” dialogue box pops up twice, once asking you if you want to download postps.php, and then asking you the same question, but with the correct PDF filename that you would have expected the first time around. This behaviour is caused by IE’s internal MIME detection routines, which are unable to determine the correct MIME type until after they have started downloading the file. Since the browser displays the first download dialogue after the headers have been received, but before the content has begun streaming, it does not yet know that the PHP file is actually outputting PDF

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FEATURES

Writing a Web-Based PDF Converter

code—and not just “pretending” to do. Thus, the file type other than PDF, the browser will not know any browser finds itself having to deal with a file that the “pre-set” way of handling it and will automatically ask server claims is a PDF file (through the Content-Type for the user’s intervention. header), while at the same time asking that—gasp!—it The filename’s extension has also changed from be downloaded as an attachment rather than by using “.pdf” to “.pdf%20”, which is the URL-encoded version Acrobat’s OLE component that would display the PDF of “.pdf” with one space character appended at the file directly in the browser. Sounds complicated? Well, believe it or Tells Ghostscript to output a PDF file. not, all this is actually done on purpose as a Ghostscript supports several ""virtual “security measure”, least you could actualsDevice=pdfwriter devices"", including jpeg, png, Postscript ly trick someone into downloading a virusand Encapsulated Postscript (EPS). laced executable camouflaged as an innocuous PDF file. Sadly, this is not normal Indicates that Ghostscript should output behaviour—according to the Internet stanr300 a document at a resolution of 300 dots dards, the browser should first set the conper inch. tent type based on the headers and then handle the file at a later stage. sOUTPUTFILE= Indicates the name of the output file There is, unfortunately, no way to fix this problem in a completely satisfactory way. Causes Ghostscript not to pause dNOPAUSE We could, for example, make the output between one page and the next PDF file itself available for direct download by the browser. However, this would cause two issues: first, by default the browser will attempt to end. When Internet Explorer detects the new extenopen the file using Acrobat’s OLE reader directly within sion, it does not recognize that the space bears no sigIE’s window. If your users are creating their PDF files for nificance and, despite the fact that the data stream the a purpose other than viewing them—such as mailing server outputs matches the PDF format to the letter and them to a client of publishing them on a website—this that our script is forcefully setting a content type of can be quite annoying and confusing to them, since “application/pdf”, determines that the file it is receiving they would have to use the reader’s Save As button is of an unknown type. If you now try to open the file, you will notice that (because the File menu is Internet Explorer’s and it does not allow for the save function) to store the file on their Internet Explorer asks you which program you want to hard disks. At the same time, making the files available open it with. All you need to do is simply choose your for direct download would force you to open a whole favourite PDF viewer and make sure that the Always use folder of data to public access, and that would open up this program to open these files check box is set, and Internet Explorer won’t bother you again, always openpotential security holes. Since the problem is mainly caused by the fact that ing your converted PDF files through the correct appliwe’re trying to force Internet Explorer to do something cation. The interesting part of all this is that, even with our PDF file that it doesn’t want to do (that is, to though Internet Explorer does not recognize the space save it to a file rather than display it in it window), in the file’s extension, it will save it using correctly as another possible solution is to trick IE into thinking that “.pdf”, since trailing spaces in a file’s name have no the file it is downloading is not a PDF file. This would meaning as far as the operating system is concerned. You will also notice that we have not changed the cause the browser to ask the user for directions—and only once. However, it has to be done in a way so that content type header. This is because Internet Explorer’s when the user actually saves the file to his or her hard behaviour is aberrant, and another browser will base its drive the browser will do so using the correct “.pdf” findings on the content type provided by the server, and handle your PDF files correctly only if the content extension. Accomplishing this feat requires just a very quick type header is properly set. change to our Content-Disposition header on line 43 of postps.php: header (‘Content-Disposition: filename=”’. $_FILES[‘infile’][‘name’] . ‘.pdf%20"’);

As you can see, this line does not indicate that the file should be treated as an attachment any longer (that’s what was causing the download popup to come up twice). That’s because, since we’re going to specify a

December 2002 · PHP Architect · www.phparch.com

php|a

Marco Tabini is co-editor of php|architect. He spends most of his time lurking around on the PHP mailing lists and on the php|a website doing is best to confuse fellow programmers who are in trouble. You can reach him at [email protected].

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FEATURES

Directing Mail With qmail’s maildirs By Jonathan Sharp Take advantage of maildirs to store you email using mailDirector and a little php magic.

I

have used various mail clients over the years, none of which have seemed to fit me perfectly. In the past, I have enjoyed the simple interface of Microsoft Outlook Express but loathed the security issues engrained in it. Pine, Mutt, KDE Mail and Mozilla Mail are just a few of the other solutions available, but I feel disconnected from my mail when they hide it in strange formats (such as mbox). Have you ever tried writing a script to archive your mail every month when it is in a mbox file? (I suggest you don’t).

I have used various mail clients over the years, none of which have seemed to fit me perfectly. The use of maildirs for mail storage has been around for quite some time. They are used by the qmail and courier-imap packages. In continuing my quest for the perfect mail application, I have found many opensource projects that support either POP3 or IMAP but are not intended to be a primary mail client. Therefore, I set forth to developing a web-based mail client that stores its mail in maildir format, and MailDirector was born. As an added bonus, MailDirector is also compli-

December 2002 · PHP Architect · www.phparch.com

mented by a simple interface with three panes for folders, folder listings and reading messages. Maildirs My choice for using maildirs for the storage layer was based upon my previous experience working with qmail, as well as another script I wrote that archives a mailing list locally. Maildirs were developed by D.J. Bernstein (http://cr.yp.to/proto/maildir.html) to provide reliable storage and delivery. One noteworthy advantage is that maildirs work over nfs without filelocking. Maildir stores messages in individual text files in one of three directories: cur, new, or tmp. New messages are downloaded from the server and put into tmp and then moved to new once they are verified. The mail client then moves them from new to cur as it processes them. A message filename consists of one of three parts: unix timestamp, pid or pid_count as to not repeat within 1 second, and the hostname. These are separated by a dot (Example: 1033929641.20384_731.zion). Then the file is just the raw text of the email. REQUIREMENTS PHP Version: 4.0 and up O/S: Tested on Linux but should work on windows Web server: Apache 1.3.27 (or around that) Support Tools: N/A

55

FEATURES

Directing Mail With qmail’s maildirs

A Few Limitations As I was writing the client for this article, there were a few limitations that I ran into. The first issue I ran into was ownership of the mail/maildirs. I tried various combinations of user and group settings but ended up giving ownership to the user that Apache runs under. Since mailDirector is intended to be more of a single user application, I do not mind having this limitation as I intend to run mailDirector locally on my workstation. Another disadvantage of using maildirs instead of, say, a mysql db is that it is hard to sort mail with any speed. The current version of mailDirector just sorts mail by the newest message first. A solution to this would be to integrate some form of caching or indexing on messages, which, however, would be beyond the scope of this particular article. One final limitation worth noting is that, currently, all mail must reside under one root folder. (This is easily worked around by symlinking to other directories if needed). One design choice that I made was to skip any form of user authentication (on my installation of mailDirector this is handled by apache’s htauth features), although it should be relatively easy to add it in the future. Existing Resources I have used the Smarty template engine on various projects for quite some time now and used it again in mailDirector. It provides an incredibly simple method for abstracting html out of your applications. Another project that I take advantage of is phpmailer (http://phpmailer.sourceforge.net), which fulfills the role of sending e-mail through an SMTP server. You will probably want to use the class included with my source (which you’ll find in this month’s code) as I added a line to save the raw text of a message after it was sent (see line 454 on class.phpmailer.php). mailDirector Layout I started tackling mailDirector by writing two objects to handle the interaction with maildirs. The first, imagListing 1 1 getNew()); 9 10 $oMessage = $oMaildir->fetchMessage($mid); 11 $oMessage->moveCur(); 12 // Mark it as replied 13 $oMessage->setReply(true); 14 ?>

December 2002 · PHP Architect · www.phparch.com

Figure 1: myConfig.conf [default] pop3 = mail.sharpmedia.net smtp = localhost mail = /home/js/mailDirector inbox = /Inbox sent = /Sent draft = /Draft trash = /Trash [myPop3Account] name = Jonathan Sharp address = [email protected] user = jsharp password = myPassword alias = [email protected] alias = [email protected] inbox = /jsharp ; Full path to sent folder would be: /home/js/mailDirector/jsharp/Sent sent = /jsharp/Sent [anotherPop3Account] name = Joe User address = [email protected] pop3 = mail.joe-smith.com smtp = smtp.joe-smith.com user = joe password = "my secret" inbox = /joeuser

inatively called maildir, takes care of listing files that reside within the new, cur, or tmp folders. It also has a method to return any child folders. This object is accompanied by maildirMessage, which handles interaction with a specific message file itself. It allows for you to easily move a message from new to cur by calling the moveCur() method, for example. Similar methods exist for setting the info flags (such as R which stands for Reply), as you can see in Listing 1. Two methods worth mentioning in maildir are _prepFile() and _prepPath(), which return a formatted string based on a variable number of arguments passed to them. They also strip out relative path information (such as ../) for added security (see Listing 2). Having written these two objects, it was time to tackle the application as a whole. First on the list was to write two more objects named mdMaildir and mdMaildirMessage which extended their respective parent classes. These two classes provide features specific to mailDirector, such as managing attachments for composing messages and allowing for naming of maildirs (by creating a .name file in a maildir). Next, I set up the mailDirector object, which is responsible for loading the config file and returning a root folder from which all other objects are created. The config file itself is quite self-explanatory (see Figure 1). If you browse through the mailDirector class you’ll notice that config and default are both set to null initially. This allows for not loading the config file until

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FEATURES

Directing Mail With qmail’s maildirs Listing 2

1 _prepPath('/path/to/my/home/dir', '../.././other/path'); 9 10 // Returns: /path/to/my/home/dir/other/path/ 11 $path = $this->_prepPath('/path/to/my/home', '/dir', 'other//', 'path'); 12 } 13 } 14 15 ?>

needed and detecting when it has been loaded. Please do keep in mind that you will want to either move the configuration file to a folder that is not accessible through the web browser or protect it using Apache’s security features. Otherwise, pretty much anyone with access to your web server will also be able to view all your e-mail accounts with their respective usernames and passwords. The next object I wrote was message, which handles parsing of raw emails and decoding mime attachments. I followed this by digging up a pop3 object that I had written sometime ago for another project. Continuing on, I downloaded the latest smarty (http://smarty.php.net) and phpmailer (http://phpmailer.sourceforge.net) and wrote an extension class for each (style extends smarty, mailer extends phpmailer.) One other object to note is applog which contains functions to writing messages to a log file. These functions provide a place to tie in your own logging system if needed. Figure 2 contains a quick review of the objects I wrote before we go on to the application’s interface.

The Interface The first objective was to get the folder browser up and running (folders.php). The code for printing out the folder tree is quite short as a result of carefully defining our objects (Listing 3). Folders.php starts off by including the mailDirector object and then requesting our root folder object. I wrote a simple recursive function, printFolders(), that walks the folder tree. The method fetchFolders() that is defined in the maildir class is what returns a list of child folders for the current folder. You can take a look at folders.tpl and foldersItem.tpl for how the html is structured; for this version of mailDirector I have chosen not to show a message count next to the folders, but this is easily added. The next step was to write listing.php (Listing 4), which would display the results of getMessages() on a folder object. It is quite similar in structure and lenth to folders.php, but two points worth noting are the use of array_split() to page through messages and

Figure 2 applog

Provides logging services to a file

mailDirector

Handles parsing of the config file and also creates our root folder object (fetchFolder() method)

maildir

Class that interfaces directly with maildirs

mdMaildir maildirMessage

Extends maildir and adds extensions specific to mailDirector such as the .name Manages a message within a maildir and allows for changing of attributes Extends maildirMessage and adds methods specific to mailDirector such as fetchIndex() Handles parsing of raw emails and headers Provides smtp mailing services Extends phpmailer Provides pop3 access to downloading mail Provides abstraction of html Extends smarty to set the template directory

mdMaildirMessage message phpmailer mailer pop3 smarty style

December 2002 · PHP Architect · www.phparch.com

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Directing Mail With qmail’s maildirs Listing 3

1 assign('folder', $obj); 10 11 $folders = $obj->getFolders(); 12 13 if ( is_array($folders) ) 14 { 15 $children = ''; 16 foreach ( $folders AS $f ) 17 { 18 $children .= printFolders( $obj->fetch($f) ); 19 } 20 21 $style->assign('children', $children); 22 } 23 24 return $style->fetch('foldersItem.tpl'); 25 } 26 27 28 $oMD = new mailDirector(); 29 $oRoot = $oMD->fetchMaildir(); 30 31 $oStyle = new style(); 32 $oStyle->assign('folders', printFolders($oRoot) ); 33 $oStyle->display('folders.tpl'); 34 ?>

FetchIndex(), which returns an array full of elements that are used when displaying a message listing. FetchIndex() actually parses a message’s headers each time a folder is clicked on. Despite all this, however, I have not noticed any large delay in speed, especially when only listing 100 messages at a time. The listing

One of the most challenging parts of this project was writing the compose.php script, which handles email composition. also makes use of some Javascript to handle loading a message into the message frame. The next portion that I tackled was read.php. I plan on developing this out as time goes on (maybe in a future article), but for now it highlights replies and provides some other formatting to spruce up messages. I make a call to htmlentities() to disable any and other tags that people like to plant in messages to see when I read them. December 2002 · PHP Architect · www.phparch.com

The Biggest Challenge: Attachments One of the most challenging parts of this project was writing the compose.php script, which handles email composition. The first issue to arise was attachments. How do you effectively add/remove attachments without refreshing the current screen and/or using a lot of Javascript code? The solution I came up with was to use an inline frame to manage the attachments. When you upload a file, it adds it to an array that gets serialized and, when the message is sent, is unserialized and attached. The compose script also does inline quoting in replies as well as attaching messages to be forwarded. I integrated Phpmailer here to send mail, a task that was easily accomplished by using the simple api provided by the class. Let There Be Mail! So, now we have a wonderful mail client that is wonderful at sending mail and reading it, but can’t download it yet. That is exactly what getmail.php does. It connects to a pop3 server as specified for each of our accounts and downloads mail into the inbox that is associated with that account. At this point, our application is completely devel-

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FEATURES Additional Resources mailDirector http://www.sharpmedia.net/mailDirector/ Maildir http://cr.yp.to/proto/maildir.html

Directing Mail With qmail’s maildir maildirMessage. Both objects were written specifically to be reused as other projects come along. As more time allows for further development on mailDirector, one key feature that would be of great value is filtering support for messages as they’re downloaded. Still, we can now take advantage of maildirs to create a complete PHP-based mail application. Until next time, happy coding!

PHPMailer http://phpmailer.sourceforge.net Smarty Template Engine http://smarty.php.net

php|a

Jonathan has worked on various commercial web applications using PHP over the past few years. He currently calls Seattle home, where he is employed for a small software company. In his free time he enjoys photography, recreational coding and a good Sunday afternoon nap. He can usually be spotted on the php mailing lists looking at the lighter side of coding. You reach him at [email protected].

oped, and our simple mail client should be able to send and receive emails with attachments. Having completed mailDirector to the point in which it is functional and can be easily built upon, we also have some new objects to add to our toolbox, maildir and Listing 4

1 fetchMaildir($folder); 12 13 /* Do we need to expunge? */ 14 if ( $_REQUEST['A'] == 'expunge' ) 15 { 16 $expunge = $oMaildir->expunge(); 17 } 18 19 /* Limit number of emails to show */ 20 $listing = $oMaildir->getMessages(); 21 $listing = array_reverse($listing); // Reverse the listing so the newest ones are first 22 $listing = array_slice($listing, $offset, $size); 23 24 $messages = array(); 25 foreach ( $listing AS $mid ) 26 { 27 $oMessage = $oMaildir->fetchMessage( $mid ); 28 $messages[$mid] = $oMessage->fetchIndex(); 29 } 30 31 /* Display the listing */ 32 $oStyle = new style(); 33 34 $total = $oMaildir->getNumMessages(); 35 36 $oStyle->assign('expunge', $expunge); 37 $oStyle->assign('total', $total); 38 $oStyle->assign('size', $size); 39 $oStyle->assign('next', $offset+$size); 40 $oStyle->assign('prev', $offset-$size); 41 $oStyle->assign('end', ($total - $size) ); 42 43 $oStyle->assign('folder', $oMaildir); 44 $oStyle->assign('messages', $messages); 45 $oStyle->display('listing.tpl'); 46 ?>

December 2002 · PHP Architect · www.phparch.com

60

REVIEWS

REVIEWS

Reviewed For You

Zend Performance Suite by Zend Corporation

Zend Performance Suite 2.5 Zend Corporation Price: $490-$2,700 US

I

n the world of IT “scalability” is the buzzword that everybody speaks but that most people consider a “happy problem”. “Sure, you need to build scalable systems, but that’s something we’ll worry when we have the problem” is the mantra, with the added concept that, if a web application is having a scalability problem because of excessive traffic, it means that it’s doing well, and that “is good”. Of course, happy problems tend to make really unhappy customers, and unhappy customers tend to make IT people lose their jobs. Luckily, PHP has been built with a good deal of scalability in mind—its very open-source nature ensures that the functionality it provides can be dissected and evaluated for maximum performance and adapted to even the most complex hardware setups in response to high workloads. The answer to these problems, however, is not only hardware—fiddling around with your server farm should be the last act in response to a raise in your traffic. The reason for this is simple and multi-faceted. First of all, more hardware means having to invest additional money, and not just in the computers themselves (which are expensive enough), but also in the infrastructure that is needed to maintain them—more power, more space, more network equipment. Most

December 2002 · PHP Architect · www.phparch.com

importantly, however, each server added to your farm creates a layer of complexity that has significant indirect costs (you will need to spend more time maintaining it) and security risks (one more possible way for hackers to enter your systems, and more systems to monitor). The Zend Performance Suite Where performance, rather than availability, is concerned, therefore, a software solution should be the first target of improvements. The Performance Suite (ZPS), published by Zend, encompasses a wide array of tools aimed at improving the efficiency of a PHP application without requiring any changes to the source code itself, while at the same time providing an interface that is very easy to use. At the core of the ZPS are three very distinct technologies: acceleration, caching and compression. The first makes it possible to pre-compile the scripts so that the PHP engine does not have to parse and interpret them each and every time they are executed—the ZPS uses the Zend Accelerator to keep each file in a “bytecode” state, so that it can simply be run without any preliminary steps. There are, to be sure, a number of products that provide the same type of functionality, but, traditionally, Zend’s acceleration engine has been unbeatable (I guess having designed the scripting engine at the core of PHP does have its advantages!). Caching, on the other hand, is performed at the con-

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Zend Performance Suite by Zend Corporation

tent level, so that PHP scripts are not executed more than once unless the data they output changes, either automatically or in response to environmental conditions, such as user input and HTTP parameters. Here, too, the ZPS allows for a very fine level of tuning, as we’ll see in a moment. The ZPS, finally, also reduces the size of a page’s HTML output by compressing it with the ZLIB library. While this method does not always result in faster downloads (since some communication devices, such as modems, already support some level of compression), it does reduce the amount of bandwidth used by a web application—and, let’s face it, bandwidth does come at a premium these days.

any intervention, and it even downloaded our registration key from the Zend website for us. Once installed, the system ran at the first try without hiccups of any sort. This does not mean that the product is not flexible or that it doesn’t provide enough freedom of configuration—its creators just decided that all the settings should be configured from within the management console that can be accessed via HTTP. Although die-hard shell fans may think of this as unnecessary, this approach should help both inexperienced users and experts alike. The downside, of course, is that if your web server goes down, you won’t be able to do much—but, in that case, you’d have bigger fish to fry anyway.

Installation

The User Interface

We installed our copy of the ZPS on a Linux machine running Apache 1.3.27 and PHP 4.2.3 (the ZPS is not yet compatible with Apache 2). I’d have to say that the installation process, which is shell-based but uses the ncurses library to provide a more interactive and colourful interface, is one of the smoothest I’ve seen in a while. In fact, the setup program automatically recognized most of our setup parameters (such as the location of the Apache binaries and the php.ini file) without

The ZPS provides a refreshingly user-friendly graphical interface, based on the web and safely protected with usernames and passwords. This management system performs three main functions:

December 2002 · PHP Architect · www.phparch.com

- Handle all the configuration parameters - Monitor the system’s status - Perform performance tests

62

REVIEWS Included in the package is also a “Fast Track” web page that provides a step-by-step guide to maximizing the site’s performance. The Fast Track is also the main page of the management system, so that it is the first thing that appears when the suite is first installed. This makes it a bit easier to get acquainted with the product, as the reader has an immediate grasp of its capabilities and of the procedure to get them all up and running. Each of the Fast Track’s steps is explained in good detail through a simple pop-up help system. Best of all, the help also explains why each step must be undertaken—so that one doesn’t feel like a robot following a checklist that he doesn’t understand.

Zend Performance Suite by Zend Corporation bit overwhelming at first—moving the advanced options to a separate screen might have been a good idea here.

The acceleration feature made our pages up to 200% faster, while caching turned them into monsters of performance, with increases sometimes close to 1500%

Configuring the System As you can see in Figure 2, the configuration console includes a detailed group of settings, divided in the three main areas of concern of the ZTS (acceleration, caching and compression). Any of the three components can be turned on and off, and several aspects of the acceleration and content caching engine can be configured. In my opinion, however, most people will be interested in simply being able to enable or disable individual components, so that this approach can be a

December 2002 · PHP Architect · www.phparch.com

You will also notice that the content caching engine, as I mentioned above, can be set to determine how a particular script should be cached based on certain environmental parameters, such as server variables, the query string or cookies. This can be done either globally or on a file-by-file basis through the File View screen. Keeping an Eye on it The ZPS’ management tool includes a monitoring

63

REVIEWS facility that makes it possible to review the status of each file that is being cached by the system, as well as provide statistics with regards to the average usage of each script. This is useful not only because the caching engine itself uses an algorithm that is based on the popularity of each script, but also (from a human standpoint) because it gives a clear overview of how the site’s pages are normally utilized. What’s more, the system also provides a sturdy testing facility for determining how the performance of each page—or of the site as a whole—is affected by the ZPS’ components. Thus, it is possible to load-test any portion of a website, or to verify by how much the compression functionality reduces the size of a particular script. Squeezing the Last Drop Out of php|a To test how good the ZPS really is, we installed it on one of our development servers, and load tested the php|a website with it. The results were quite impressive: the acceleration feature made our pages up to 200% faster, while caching turned them into monsters of performance, with increases sometimes close to 1500%. The latter was largely due to the fact that our develop-

December 2002 · PHP Architect · www.phparch.com

Zend Performance Suite by Zend Corporation ment servers connect to our live database through an SSH tunnel, which is inherently slow. Turning the cache on removes the database from the picture entirely, so that our pages gain in speed enormously. This is probably not an entirely realistic scenario in the case of a live server, but, if your database does not reside on the same server as Apache, you are bound to see some major speed improvements. A Final Note Is the ZPS worth its money? After all, even though its cost/performance ratio is much lower than a hardware solution, there are several open-source alternatives that provide similar functionality. Our answer will have to be yes. The ZPS performs better, on average, than any of its competitors, and does so in a completely integrated way. What’s more important, however, is that the ZPS is a complete suite of applications that requires minimal installation and configuration efforts. If you consider that you might be installing it at a time in which you are under great pressure to resolve a crisis brought on by a sudden surge in traffic, its simplicity is just priceless. php|a

64

TIPS & TRICKS

TIPS & TRICKS

Tips & Tricks By John W. Holmes

1. Check Your Subject

Q

uite a few web sites have pages through which you can send an e-mail to someone. These can be used to contact the site administrator, send a message out to other users, or many other purposes. Often the goal of the contact form is to hide the e-mail address of the recipient. This can be for convenience (to prevent spam) or for security (protecting the identity of recipients). If your site is just using a normal text block for the user to enter the subject of the message in, you may be unwittingly allowing your visitors to add additional headers to the e-mail message. The user can download (save-as) your form and modify the area into a element. Then, he or she can enter a "subject" like the one shown in Figure 1. Figure 1<br /> <br /> the Bcc: and Reply-To: headers are also added to the message. So now the malicious user has included themselves on the contents of the message, can see who all of the other recipients were, and the end user is unaware that there is now a bad or altered Reply-To: address.<br /> <br /> If your site is just using a normal <input> text block for the user to enter the subject of the message in, you may be unwittingly allowing your visitors to add additional headers to the e-mail message.<br /> <br /> This is my subject Bcc: my_email@my_domain.com Reply-To: bad_email@evil_domain.com<br /> <br /> When this subject is inserted into PHP's mail() function: mail($to,$subject,$message,$headers);<br /> <br /> December 2002 · PHP Architect · www.phparch.com<br /> <br /> Now, this may not matter on a simple web page where people are sending you questions about your cat, because all this will do is give the user a copy of the message they just typed. But imagine a web page that allows Alcoholic Anonymous users to contact and email each other anonymously. Now malicious users can Bcc: themselves on messages and see who all of the recipients are and possibly intercept replies to the mes-<br /> <br /> 65<br /> <br /> TIPS & TRICKS sage if the altered Reply-To: address is not noticed. Or, how about a lot of the forum scripts that are available that let you e-mail another user, but do not show you their e-mail address. Now you can Bcc: yourself on the message you send them and find out their actual e-mail address. The recipient of the message will not know unless they examine all of the e-mail headers closely. The bottom line is that you are allowing the user to put in unchecked headers to your mail messages. The solution to this is to filter the subject you receive from your text box for new line ("\n") characters. You can remove everything after the first new line with: substr($string,0,strpos($string,"\n")-1)<br /> <br /> Another option is to just tell the user that there has been an error if a new line is detected and attempt to save as much information about the user as you can, for future reference (as long as that is in compliance with your privacy policy). 2. Power Slows You Down If you don't know already, Regular Expressions are a powerful tool that every programmer should be familiar with. Regular Expressions will allow you to define complex patterns used to search text. However, as powerful as they are, they can be slower than other functions that provide a more basic functionality. PHP provides functions such as preg_replace() to replace a pattern with another and preg_split() to split a string into an array based upon a pattern. However, if you're not using any actual regular expression patterns and are looking to replace a specific word or split on a single character, then regular expression functions are overkill. You will save processing time by using str_replace() instead of preg_replace() and explode() instead of preg_split(). However, since str_replace is case sensitive, if you want a case insensitive search and replace, then it is faster to use preg_replace() instead of a homegrown function. You can make use of an "i" as a pattern modifier to make the replacement case insensitive. Figure 3 ; Sample configuration file ; Comments start with ';', as in php.ini [section_one] foo = bar option = 5 [section_two] path = "/home/groups/me/" database = mysql<br /> <br /> December 2002 · PHP Architect · www.phparch.com<br /> <br /> $c = str_replace("/a/i","b",$string);<br /> <br /> Will replace all occurrences of "a" or "A" in $string with "b". 3. Make Your Own .ini File PHP has a function, parse_ini_file(), that will read a text file and make an associative array out of the settings defined in it. What this means is that you can have a file similar to php.ini to define the configuration parameters used by your application. Figure 3 Array ( [foo] => bar [option] => 5 [path] => /home/groups/me/ [database] => mysql ) Array ( [section_one] => Array ( [foo] => bar [option] => 5 ) [section_two] => Array ( [path] => /home/groups/me/ [database] => mysql ) )<br /> <br /> The function can be called with one or two arguments. The first argument is required and is a path to the file you want to parse. An example file is shown in Figure 3. The function returns an associative array that can be returned in two formats, depending on the second argument for the function. The second argument controls whether sections within the file will be parsed separately. Passing FALSE, which is the default, as the second argument will produce an array such as the first one shown in Figure 4 from the file in Figure 3. The sections are ignored and you are returned a one dimensional array. Passing TRUE for the second argument will make PHP return a multi-dimensional array based on the sections of the file. The second array in Figure 4 is an example of an array returned with the second argument of parse_ini_file() as TRUE. The file that will hold your configuration values is a plain text file that can be given any extension. If it is given a .php extension, then it will be served up as plain text to the browser if it is ever called on its own. Your configuration values can then be viewed by any-<br /> <br /> 66<br /> <br /> TIPS & TRICKS one and passwords or other sensitive information could be exposed. The best solution to prevent this is to store the document outside of the web root, so it can not be called through a browser. If this can not be done, then placing an .htaccess rule, or whatever mechanism your web server allows for this purpose, that will deny access to the extension you've chosen to use is another option. If you still can not do that, a third option would be to place a line such as the following at the beginning of the file and give it a .php extension<br /> <br /> include a .js JavaScript file from their own server and have it execute on your own. The user could redirect the user to their own site and have false content made to look like your site, or steal your users' passwords, as well as "hijack" their sessions, with potentially disastrous results. So, how do you solve this? By remembering the mantra of web programming: Never Trust User Input. When asking for a Name, never assume the user is going to give you name, make sure it is one. This is where regular expressions would come in handy as you can make sure the content is just letters.<br /> <br /> ; <? exit; ?><br /> <br /> The line will be ignored as a comment when parsed with parse_ini_file(). When the file is parsed by PHP, however, it will exit on the first line and not show any of the remaining information in the file. 4. Cross Site What? Perhaps you've heard the buzz words "Cross Site Scripting". It's often abbreviated as XSS and can be a real pain to a developer if you're not aware of it. It can be used in a variety of ways, but a simple example would be a script where you ask the user for their name, then display a welcome page with their name on it. (editor's note: anybody caught attempting to test XSS on the php|a web site will receive his or her next copy attached to a brick with no postage—Mt.) <input type="text" name="user_name><br /> <br /> Perhaps you've heard the buzz words "Cross Site Scripting". It's often abbreviated as XSS and can be a real pain to a developer if you're not aware of it. Another option, when accepting large amounts of text that you don't want to allow HTML content within, is to use strip_tags(). This function will remove any HTML that you don't want allowed. Say you have a text area where you want to allow your users to be able to use <strong> and <em> tags, but no other HTML. You can filter the user's input by using the following:<br /> <br /> The welcome message would be displayed with echo "Welcome to my page, {$_GET['user_name' ]}";<br /> <br /> What's the harm in that? Well, what if the user types the string <img src="dirty.jpg"><br /> <br /> as his name? Think it'll look funny as a name? Actually, it'll be evaluated as HTML by the browser and the image will show up on your site. If you're thinking that this problem only occurs when that specific user looks at your page, think again. All that user has to do is send out an e-mail asking people to take a look at the "awful pictures" on your respectable site by clicking on a link like www.yourdomain.com/page.php?user_name=dirty.j pg Again, this is just a basic example. The user could<br /> <br /> December 2002 · PHP Architect · www.phparch.com<br /> <br /> $good_string = strip_tags ( $user_input , "<strong><em>" );<br /> <br /> Now you can safely display $good_string back to the user, or otherusers, without fear of something bad being passed through. An even better option, in my opinion, is to use either the htmlentities() or htmlspecialchars() functions. These will convert special HTML characters like < and > (among many others) into entities like < Figure 7 <input type="text" name="test" value="<tag example>"> <input type="text" name="test2" value="An example with "quotes""><br /> <br /> and >. What this will do is to output any "bad" input in a format that will not be interpreted as HTML but shown by the browser exactly how it was entered. For<br /> <br /> 67<br /> <br /> TIPS & TRICKS example, <img> will show as <img> in the source, but as <img> when it's rendered. The browser will display <img> literally, instead of evaluating it as an actual image tag. The benefit of using this over strip_tags() is that if the user types in something innocent like <smile>, strip_tags() will remove it, whereas htmlentities() will just display it to the user, but not evaluate it as HTML. It's dependent upon your application whether you apply these function before you store the data or before<br /> <br /> instead of the code. The second input box in Figure 7 shows how you would include a double quote (") within your text box when the value of the box is delimited by double quotes. If you tried to use a value such as value="An example with "quotes""<br /> <br /> then the second double quote would be interpreted as the end of the string. The value in the text box<br /> <br /> Figure 5 $str = "I am going to be 100 years old on the 17th of November, 2002"; $new_str = preg_replace("/([0-9]+)/e","'0x'.sprintf('%04X',$1)",$str); echo $new_str;<br /> <br /> Output: I am going to be 0x0064 years old on the 0x0011th of November, 0x07D2<br /> <br /> Figure 6 $s = "I am going to be {a} years old on the {b}th of November, {c}."; $a = array( "a" => "one hundred", "b" => "seventeen", "c" => "two thousand two"); $z = preg_replace("/\{([a-z]+)\}/e","\$a['$1']",$s); echo $z;<br /> <br /> Output: I am going to be one hundred years old on the seventeenth of November, two thousand two.<br /> <br /> you display it. If you ever use your data as plain text, such as invoices, etc, that is not presented as HTML, then you will not want to apply these functions before you store your data. Otherwise your invoices will have < instead of the actual < character. You can use the functions as you display the data in HTML, though, so that any malicious HTML code is not evaluated. If you only use an HTML interface for your data, you can apply these changes before you store the data. This way, the function is only called once upon storing and not every time the page is displayed. You may be worried about what happens when you want to edit the text later on through a web interface. If you put this into a text box, won't you have a bunch of < and > to edit, instead of the actual characters you wanted? Actually, no, you won't. If you have a text box like the one shown in Figure 7, then the HTML entities will show up in the box as the actual < and > characters, December 2002 · PHP Architect · www.phparch.com<br /> <br /> would show up as 'An example with 'and the 'quotes""' would be ignored as an unknown attribute. 5. The Good Kind of "e" When using preg_replace(), you can use "e" as a pattern modifier. According to the manual, "If this modifier is set, preg_replace() does normal substitution of backreferences in the replacement string, evaluates it as PHP code, and uses the result for replacing the search string." What does mean? PHP will evaluate your replacement string as PHP code, similar to using eval() and you can use the patterns you matched in your string in this code. Take Figure 5 as an example. Say you wanted to replace every number in a string with it's 4 digit hexa-<br /> <br /> 68<br /> <br /> TIPS & TRICKS decimal equivalent. The pattern "/([0-9]+)/" matches the numbers 100, 17, and 2002. Since the 'e' modifier is being used, "'0x'.sprintf('%04X',$1)" is evaluated as PHP code, where $1 is the first backreference. So, the "replacement string" takes the string '0x' and the 4 digit hexadecimal (%04X) value of each number and replaces the original number. Figure 6 shows how you can use this functionality to make a simple template engine. Here, $a is an array whose keys are represented by placeholders in the "template" string. The preg_replace() looks for a series of lowercase letters (use an 'i' modifier to make it case insensitive) surrounded by { and }. It will replace the text matched in the original string with the corresponding element of $a. So when "{a_key}" is matched, it is replaced with the value in $a['a_key']. There are other methods to achieve this very result, and probably some of them are better than using the e modifier, but this is one simple example for you. 6. Variable Functions You can use a variable as the name of a function.<br /> <br /> December 2002 · PHP Architect · www.phparch.com<br /> <br /> $a = 'str_replace'; $b = $a('%body%','black','<body bgcolor = "%black%">');<br /> <br /> In that example, $a() is actually calling the str_replace() function. This can be useful for validation classes where you need to validate input based on a certain "mode." Rather than using a list of switch cases to choose which function to call, you can pass the function name in $mode, and call it as $validate_value = $mode($unvalidated_value); Be especially careful you know what $mode is set to though, or are validating it if it's coming from the client. Do you have some better tips and tricks than this that you'd like to share with the PHP community? e-mail me at tipsntricks@phparch.com and I'll try to include them in the next available issue. php|a<br /> <br /> John Holmes is a First Lieutenant in the U.S. Army and a freelance PHP and MySQL programmer. He has been programming in PHP for over 4 years and loves every minute of it. He is currently serving at Ft. Gordon, Georgia as a Company Commander with his wife, son, and another one on the way.<br /> <br /> 69<br /> <br /> BOOK REVIEWS<br /> <br /> BOOK REVIEWS<br /> <br /> For Your Reading Pleasure<br /> <br /> PHP Programming for Windows by Andrew Stopford Published by New Riders ISBN 0735711690 US $39.99 Canada $62.99 UK £30.99<br /> <br /> It’s refreshing, for a change, to see a book that is dedicated to PHP developers who work with Windows. At the very least, a book like PHP Programming for Windows (PHPPW from now) is a clear sign of the fact that there is interest, among Win32 users, into going beyond what technologies has to offer and reach out for the power of PHP. Without trying to be an all-encompassing PHP bible, PHPPW features a very solid set of Windows-related topics, including a lengthy explanation of how PHP can be installed on a variety of web server platforms—not just Apache, but also IIS 4.0/5.0 and Personal Web Server. As the PHP documentation is rather sketchy on this subject, and server technology can be pretty picky at times, this section alone is worth the price of the book, in our opinion. After reading through this book,<br /> <br /> December 2002 · PHP Architect · www.phparch.com<br /> <br /> we doubt that anybody would have much trouble getting PHP going on any Windows-based box, regardless of the web server software and installation method used. PHPPW also covers the integration of several key Microsoft technologies with PHP, such as COM, MSXML, ADODB, .NET and WDDX—the latter one, in particular, lets you share session state variables (as well as other information) between PHP and ASP. Most developers who have agonized over the official PHP documentation will also find the portion on SOAP and web services very useful (we did). Unfortunately, there is no mention of how PHP can be used as a shell development tool. As much as Windows programming is generally GUI-oriented, PHP offers, we think, a much superior alternative to the Windows Shell. As such, the book misses a great opportunity by not explaining how it can be taken advantage of for batch processing through the good old DOS prompt or the Windows scheduler. The book is generally well-written, with a good attention to detail and a clear and easy-to-read style. The best thing about is that it stands apart from many of its counterparts in that it offers clear insight on matters that are usually difficult to penetrate, not because they are very complex, but because they are poorly documented. We think that this characteristic alone adds a significant amount of value to PHPPW, as it provides its reader with information that is not quite that is easy to find by just running a couple of search queries through Google.<br /> <br /> 70<br /> <br /> BOOK REVIEWS If anything, our only gripe about PHPPW is that it walks a dangerous line: a very Microsoft-specific PHP website will not run very well on other platforms, obviously. As time progresses and technologies mature it pays off to create web applications that are as operating system-agnostic as possible, so that they can take advantage of whatever technologies are available on any particular platform without requiring a complete rewrite every time. The book could have benefited, in our opinion, from a more open look at how Microsoft technologies can be taken advantage of in a Windows environment without compromising the portability of a web system that is based on them. However, this is altogether a small detail—let’s just say that it leaves all portability-related decisions up to the individual developer—that does not compromise the true value that this book can have for a Windows programmer.<br /> <br /> PHP Advanced For The World Wide Web By Larry Ullman Peachpit Press ISBN 0201775972 US $29.99 Canada $44.95 UK £22.99<br /> <br /> At last, a PHP book that is not going to break the bank! Larry Ullman and the folks at PeachPitt press have done an excellent job with PHP Advanced For the World Wide Web in presenting a rather complete tutorial of the PHP language under a new light. This book uses a particularly good format—for one thing, it’s laid out on two columns (not unlike php|a, and that’s a clear sign that we have a winner on our hands). What’s more, its pages are also in colour (something very unusual for technical books, whose pages, with the exception of the cover, are usually printed in black-and-white. Luckily, the colours are actually used very wisely to highlight portions of code or printouts that are of particular interest to the topic that the author is currently covering. This makes for a very pleasant read, both if you’re trying to assimilate the book as a whole and if you’re just using it as a reference. Larry Ullman’s opus covers a wide variety of topics, but rather than taking the approach of simply providing a reference for all the functionality provided by PHP, its contents are divided in thematic areas, such as ecommerce, security, database, XML, PDF and image December 2002 · PHP Architect · www.phparch.com<br /> <br /> For Your Reading Pleasure manipulation, and so on. Each topic is analyzed in a great amount of detail, using plenty of examples as a way to make concepts easier to assimilate. Our favourite sections of this book are those dedicated to graphical imaging and PDF generation. These are two topics that are frequently discussed on the PHP mailing lists, but not frequently enough to create a solid base of archival information usable by everybody (on the other hand, there is plenty of archival data on the register_global problem, but nobody ever seems to care to search for it!). Ullman dedicates almost seventyfive pages to the GD library and the PDFlib extension, going into extreme detail and providing a huge amount of examples. The major flaw of PHP Advanced is that it’s extremely PHP-centric. While you would probably expect a book about PHP to be, it sometimes (but not often) misses the opportunity to discuss the integration with other technologies in detail, providing summary descriptions of other platforms. As an example, the chapter on COM, which is only about ten pages long, describes the Component Object Method as follows:<br /> <br /> At last, a PHP book that is not going to break the bank! Larry Ullman and the folks at PeachPitt press have done an excellent job with PHP Advanced For the World Wide Web. “Microsoft has defined every function and attribute that an application—such as Word or Excel—has as an object with methods and properties.” This is, in our opinion, a rather simplistic view of what COM is and what it has to offer. Someone who is not familiar with it might discount it as yet another Microsoft buzzword, whereas it is at the very core of most of Windows’ functionality. Still, Ullman does provide, as part of the very same chapter an interesting example on how to invoke and manipulate Microsoft Word from within PHP under Windows. All things considered, this is a great book. It offers excellent features not only in its contents, but also in the way it is presented and in its very convenient price tag. php|a<br /> <br /> 71<br /> <br /> exit(0);<br /> <br /> A War With No Enemies<br /> <br /> exit(0);<br /> <br /> By Marco Tabini Looking back at what has made the news over the last month, one topic seems to forcefully spring to attention over the normal journalistic buzz. Several news outlets, in fact, have reported a generalized “alarm” over the alleged “insecurity” of opensource software. This year’s “Halloween Documents”, in which Microsoft supposedly admits that its efforts to prevail over OSS by claiming it to be unstable, poorly written and generally bad for the economy—a sort of communist specter over the software development community, were leaked at the beginning of November. I’m not a great believer in coincidences—and the sudden surge of concern on behalf of High Tech right after those documents were released does leave some room for thought. Still, that’s not what really bothers me. What does disturb me is this continuous mud-slinging activity that the commercial software community seems to have chosen as its best defense against OSS. “Don’t buy OSS because it’s evil” was the mantra for the past six months. When that didn’t work out, it became “don’t buy OSS because how can you possibly trust these communist programmers who don’t want to be paid?”. Now it’s “don’t buy OSS because it’s not secure”. How sad, then, that the sentence-of-the-day has never been “don’t buy OSS because our software is better—and here’s why.” Focusing on trying to convince IT executives that OSS is bad seems to be the best that commercial developers can do. Worse yet, the news does not come directly from the software developers, but indirectly from “focus groups” or news services that, by definition, should adopt a rule of complete transparency, if only for a matter of pure business ethics. Unfortunately, some choose selective disclosure in their efforts to demonstrate as true statements whose credibility crumbles after a bit of careful examination. In the process, they end up damaging all software— open-source and commercial. As many have come to realize, the truth lies somewhere in the middle—OSS makes more sense in some cases, and commercial applications are better suited to others. If this were an accepted fact, then the whole IT community could move on to trying to figure out how OSS and commercial applications can best survive side-by-side, with the not-so-small side effect of making everybody’s life easier. Microsoft Word is a clear example—as much as OpenOffice is a good product, it still has a lot to catch up when it’s compared against its commercial cousin. The fact that it is free does not make up for how much easier Word makes, for example, the management of multiple revisions—at least for the moment. It should be noted, in my opinion, that this attitude seems to be mostly (although not exclusively) a problem with the commercial software community, which undoubtedly feels threatened by OSS. Opensource developers, for the most part, seem to have realized a while back that good software comes in all shapes and that the best thing that can be done is to give users a choice. This could explain, therefore, why it’s easy to convert a Microsoft Outlook mailbox to Ximian Evolution or Netscape Mail, while it’s almost impossible to do the opposite, or why there is a version of Internet Explorer for Solaris but none for Linux or FreeBSD. Besides the users—who are clearly getting the short end of the stick—the party that stands to suffer the most from this approach is commercial software itself. After all, if it’s easy to move in one direction but not in the other, users won’t be able to move back to Windows once they’re on OSS. So, as it happens, the commercial software industry is fighting a war with stink bombs when no enemy is even in sight. 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