PHP5 and MYSQL Bible

John Wiley & Sons

Chapter One

This first chapter is an introduction to PHP, MySQL, and the interaction of the two. In it, we'll try to address some of the most common questions about these tools, such as "What are they?" and "How do they compare to similar technologies?" Most of the chapter is taken up with an enumeration of the many, many reasons to choose PHP, MySQL, or the two in tandem. If you're a techie looking for some ammunition to lob at your PHB ("Pointy-Haired Boss" for those who don't know the Dilbert cartoons) or a manager asking yourself what is this P-whatever thing your geeks keep whining to get, this chapter will provide some preliminary answers.

What Is PHP?

PHP is the Web development language written by and for Web developers. PHP stands for PHP: Hypertext Preprocessor. The product was originally named Personal Home Page Tools, and many people still think that's what the acronym stands for. But as it expanded in scope, a new and more appropriate (albeit GNU-ishly recursive) name was selected by community vote. PHP is currently in its fifth major rewrite, called PHP5 or just plain PHP.

PHP is a server-side scripting language, which can be embedded in HTML or used as a standalone binary (although the former use is much more common). Proprietary products in this niche are Microsoft's Active Server Pages, Macromedia's ColdFusion,and Sun's Java Server Pages. Some tech journalists used to call PHP "the open source ASP" because its functionality is similar to that of the Microsoft product-although this formulation was misleading, as PHP was developed before ASP. Over the past few years, however, PHP and server-side Java have gained momentum, while ASP has lost mindshare, so this comparison no longer seems appropriate.

We'll explore server-side scripting more thoroughly in Chapter 2, but for the moment you can think of it as a collection of super-HTML tags or small programs that run inside your Web pages-except on the server side, before they get sent to the browser. For example, you can use PHP to add common headers and footers to all the pages on a site or to store form-submitted data in a database.

Strictly speaking, PHP has little to do with layout, events, on the fly DOM manipulation, or really anything about what a Web page looks and sounds like. In fact, most of what PHP does is invisible to the end user. Someone looking at a PHP page will not necessarily be able to tell that it was not written purely in HTML, because usually the result of PHP is HTML.

PHP is an official module of Apache HTTP Server, the market-leading free Web server that runs about 67 percent of the World Wide Web (according to the widely quoted Netcraft Web server survey). This means that the PHP scripting engine can be built into the Web server itself, leading to faster processing, more efficient memory allocation, and greatly simplified maintenance. Like Apache Server, PHP is fully cross-platform, meaning it runs native on several flavors of Unix, as well as on Windows and now on Mac OS X. All projects under the aegis of the Apache Software Foundation-including PHP-are open source software.

What Is MySQL?

MySQL (pronounced My Ess Q El) is an open source, SQL Relational Database Management System (RDBMS) that is free for many uses (more detail on that later). Early in its history, MySQL occasionally faced opposition due to its lack of support for some core SQL constructs such as subselects and foreign keys. Ultimately, however, MySQL found a broad, enthusiastic user base for its liberal licensing terms, perky performance, and ease of use. Its acceptance was aided in part by the wide variety of other technologies such as PHP, Java, Perl, Python, and the like that have encouraged its use through stable, well-documented modules and extensions. MySQL has not failed to reward the loyalty of these users with the addition of both subselects and foreign keys as of the 4.1 series.

Databases in general are useful, arguably the most consistently useful family of software products-the "killer product" of modern computing. Like many competing products, both free and commercial, MySQL isn't a database until you give it some structure and form. You might think of this as the difference between a database and an RDBMS (that is, RDBMS plus user requirements equals a database).

There's lots more to say about MySQL, but then again, there's lots more space in which to say it.

The History of PHP

Rasmus Lerdorf-software engineer, Apache team member, and international man of mystery-is the creator and original driving force behind PHP. The first part of PHP was developed for his personal use in late 1994. This was a CGI wrapper that helped him keep track of people who looked at his personal site. The next year, he put together a package called the Personal Home Page Tools (a.k.a. the PHP Construction Kit) in response to demand from users who had stumbled into his work by chance or word of mouth. Version 2 was soon released under the title PHP/FI and included the Form Interpreter, a tool for parsing SQL queries.

By the middle of 1997, PHP was being used on approximately 50,000 sites worldwide. It was clearly becoming too big for any single person to handle, even someone as focused and energetic as Rasmus. A small core development team now runs the project on the open source "benevolent junta" model, with contributions from developers and users around the world. Zeev Suraski and Andi Gutmans, the two Israeli programmers who developed the PHP3 and PHP4 parsers, have also generalized and extended their work under the rubric of Zend.com (Zeev, Andi, Zend, get it?).

The fourth quarter of 1998 initiated a period of explosive growth for PHP, as all open source technologies enjoyed massive publicity. In October 1998, according to the best guess, just over 100,000 unique domains used PHP in some way. Just over a year later, PHP broke the one-million domain mark. When we wrote the first edition of this book in the first half of 2000, the number had increased to about two million domains. As we write this, approximately 15 million public Web servers (in the software sense, not the hardware sense) have PHP installed on them.

Public PHP deployments run the gamut from mass-market sites such as Excite Webmail and the Indianapolis 500 Web site, which serve up millions of pageviews per day, through "mass-niche" sites such as Sourceforge.net and Epinions.com, which tend to have higher functionality needs and hundreds of thousands of users, to e-commerce and brochureware sites such as The Bookstore at Harvard.com and Sade.com (Web home of the British singer), which must be visually attractive and easy to update. There are also PHP-enabled parts of sites, such as the forums on the Internet Movie Database (imdb.com); and a large installed base of nonpublic PHP deployments, such as LDAP directories (MCI WorldCom built one with over 100,000 entries) and trouble-ticket tracking systems.

In its newest incarnation, PHP5 strives to deliver something many users have been clamoring for over the past few years: much improved object-oriented programming (OOP) functionality. PHP has long nodded to the object programming model with functions that allow object programmers to pull out results and information in a way familiar to them. These efforts still fell short of the ideal for many programmers, however, and efforts to force PHP to build in fully object-oriented systems often yielded unintended results and hurt performance. PHP5's newly rebuilt object model brings PHP more in line with other object-oriented languages such as Java and C++, offering support for features such as overloading, interfaces, private member variables and methods, and other standard OOP constructions.

With the crash of the dot-com bubble, PHP is poised to be used on more sites than ever. Demand for Web-delivered functionality has decreased very little, and emerging technological standards continue to pop up all the time, but available funding for hardware, licenses, and especially headcount has drastically decreased. In the post-crash Web world, PHP's shallow learning curve, quick implementation of new functionality, and low cost of deployment are hard arguments to beat.

The History of MySQL

Depending on how much detail you want, the history of MySQL can be traced as far back as 1979, when MySQL's creator, Monty Widenius, worked for a Swedish IT and data consulting firm, TcX. While at TcX, Monty authored UNIREG, a terminal interface builder that connected to raw ISAM data stores. In the intervening 15 years, UNIREG served its makers rather well through a series of translations and extensions to accommodate increasingly large data sets.

In 1994, when TcX began working on Web data applications, chinks in the UNIREG armor, primarily having to do with application overhead, began to appear. This sent Monty and his colleagues off to look for other tools. One they inspected rather closely was Hughes mSQL, a light and zippy database application developed by David Hughes. mSQL possessed the distinct advantages of being inexpensive and somewhat entrenched in the market, as well as featuring a fairly well-developed client API. The 1.0 series of mSQL release lacked indexing, however, a feature crucial to performance with large data stores. Although the 2.0 series of mSQL would see the addition of this feature, the particular implementation used was not compatible with UNIREG's B+-based features. At this point, MySQL, at least conceptually, was born.

Monty and TcX decided to start with the substantial work already done on UNIREG while developing a new API that was substantially similar to that used by mSQL, with the exception of the more effective UNIREG indexing scheme. By early 1995, TcX had a 1.0 version of this new product ready. They gave it the moniker MySQL and later that year released it under a combination open source and commercial licensing scheme that allowed continued development of the product while providing a revenue stream for MySQL AB, the company that evolved from TcX.

Over the past ten years, MySQL has truly developed into a world class product. MySQL now competes with even the most feature-rich commercial database applications such as Oracle and Informix. Additions in the 4.x series have included much-requested features such as transactions and foreign key support. All this has made MySQL the world's most used open source database.

Reasons to Love PHP and MySQL

There are ever so many reasons to love PHP and MySQL. Let us count a few.

Cost

PHP costs you nothing. Zip, zilch, nada, not one red cent. Nothing up front, nothing over the lifetime of the application, nothing when it's over. Did we mention that the Apache/PHP/MySQL combo runs great on cheap, low-end hardware that you couldn't even think about for IIS/ASP/SQL Server?

MySQL is a slightly different animal in its licensing terms. Before you groan at the concept of actually using commercial software, consider that although MySQL is open-source licensed for many uses, it is not and has never been primarily community-developed software. MySQL AB is a commercial entity with necessarily commercial interests. Unlike typical open source projects, where developers often have regular full-time (and paying) day jobs in addition to their freely given open source efforts, the MySQL developers derive their primary income from the project. There are still many circumstances in which MySQL can be used for free (basically anything nonredistributive, which covers most PHP-based projects), but if you make money developing solutions that use MySQL, consider buying a license or a support contract. It's still infinitely more reasonable than just about any software license you will ever pay for.

For purposes of comparison, Table 1-1 shows some current retail figures for similar products in the United States. All prices quoted are for a single-processor public Web server with the most common matching database and development tool; $0 means a no-cost alternative is a common real-world choice.

Open source software: don't fear the cheaper

But as the bard so pithily observed, we are living in a material world-where we've internalized maxims such as, "You get what you pay for," "There's no such thing as a free lunch," and "Things that sound too good to be true usually are." You (or your boss) may, therefore, have some lingering doubts about the quality and viability of no-cost software. It probably doesn't help that until recently software that didn't cost money-formerly called freeware, shareware, or free software-was generally thought to fall into one of three categories:

* Programs filling small, uncommercial niches

* Programs performing grungy, low-level jobs

* Programs for people with bizarre socio-political issues

It's time to update some stereotypes once and for all. We are clearly in the middle of a sea change in the business of software. Much (if not most) major consumer software is distributed without cost today; e-mail clients, Web browsers, games, and even full-service office suites are all being given away as fast as their makers can whip up Web versions or set up FTP servers. Consumer software is increasingly seen as a loss-leader, the flower that attracts the pollinating honeybee-in other words, a way to sell more server hardware, operating systems, connectivity, advertising, optional widgets, or stock shares. The full retail price of a piece of software, therefore, is no longer a reliable gauge of its quality or the eccentricity-level of its user.

On the server side, open source products have come on even stronger. Not only do they compete with the best commercial stuff; in many cases there's a feeling that they far exceed the competition. Don't take our word for it! Ask IBM, any hardware manufacturer, NASA, Amazon.com, Rockpointe Broadcasting, Ernie Ball Corporation, the Queen of England, or the Mexican school system. If your boss still needs to be convinced, further ammunition is available at opensource.org and fsf.org.

The PHP license

The freeness of open source and Free software is guaranteed by a gaggle of licensing schemes, most famously the GPL (Gnu General Public License) or copyleft. PHP used to be released under both the GPL and its own license, with each user free to choose between them. This has recently changed. The program as a whole is now released under its own extremely laissezfaire PHP license on the model of the BSD license, whereas Zend as a standalone product is released under the Q Public License (this clause applies only if you unbundle Zend from PHP and try to sell it).

You can read the fine print about the relevant licenses at these Web sites:

* php.net/license/

* mysql.com/doc/en/GPL_license.html

* troll.no/qpl/annotated.h

Continues...

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Excerpted from PHP5 and MYSQL Bible by Tim Converse Joyce Park Clark Morgan Excerpted by permission.
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