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. 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 sev-eral flavors of Unix, as well as on Windows and now on Mac OS X. All projects under the aegis of the Apache Software Foundation — ncluding 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.
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