An Introduction to PHP | WebReference

An Introduction to PHP

An Introduction to PHP

This chapter is an excerpt from the book: Core PHP Programming 3/E by Prentice Hall.

This chapter introduces you to PHP. You will learn how it came about, what it looks like, and why it is the best server-side technology. It also exposes the most important features of the language.

PHP began as a simple macro replacement tool. Like a nice pair of shoes, it got you where you needed to go, but you could go only so far. On the hyperspeed development track of the Internet, PHP has become the equivalent of a 1960s muscle car. It's cheap, it's fast, and there's plenty of room under the hood for you and your virtual wrench.

This chapter lets you poke around the PHP engine, get your hands a little dirty, and take it for a spin. There are lots of small examples you can try immediately. Like all the examples in this article, you can easily adapt them to provide real solutions. Don't be intimidated if you don't fully understand the PHP code at first. Later articles deal with all the issues in detail.

This chapter talks about some things that you already know, such as what a computer is, just to make sure we're all on the same page. You may be a wizard with HTML but not fully appreciate the alien way computers are put together. Or you may find you learned all these things in a high school computer class. If you get bored with the basics, skip to another article.

1.1 The Origins of PHP

Wonderful things come from singular inspiration. PHP began life as a simple way to track visitors to Rasmus Lerdorf's resume. It also could embed SQL queries in Web pages. But as often happens on the Web, admirers quickly asked for their own copies. As a proponent of the Internet's ethic of sharing, and as a generally agreeable person, Rasmus unleashed upon an unsuspecting Web his Personal Home Page Tools version 1.0.

"Unleashed upon himself" may be more accurate. PHP became very popular. A consequence was a flood of suggestions. PHP 1. 0 filtered input, replacing simple commands for HTML. As its popularity grew, people wondered if it couldn't do more. Loops, conditionals, rich data structures— all the conveniences of modern structured programming seemed like a next logical step. Rasmus studied language parsers, read about YACC and GNU Bison, and created PHP 2, otherwise known as PHP/ FI.

PHP/ FI allowed developers to embed structured code inside HTML tags. PHP scripts could parse data submitted by HTML forms, communicate with databases, and make complex calculations on the fly. And it was very fast because the freely available source code compiled into the Apache Web server. A PHP script executed as part of the Web server process and required no forking, often a criticism of Common Gateway Interface (CGI) scripts.

PHP was a legitimate development solution and began to be used for commercial Web sites. In 1996, Clear Ink created the SuperCuts site (www. supercuts. com) and used PHP to create a custom experience for the Web surfer. The PHP Web site tracks the popularity of PHP by measuring how many different Web sites use the PHP module. When writing the second edition of this text, it seemed really exciting that PHP had grown from 100,000 sites to 350,000 sites during 1999. The most recent data show more than 10 million domains using PHP!

In 1997, a pair of Israeli students named Andi Gutmans and Zeev Suraski attempted to use it for building an online shopping cart, considered cutting-edge enough to be a university project. Shortly after they started, they stumbled upon various bugs in PHP that made them look under the hood at the source code. To their surprise, they noticed that PHP's implementation broke most of the principles of language design, which made it prone to unexpected behavior and bugs. Always looking for good excuses not to study for exams, they started creating a new implementation. In part, the task was a test of their programming abilities, in part a recreation. A few months later, they had rewritten PHP from scratch, making it a real, consistent, and robust language for the first time. Having spent so much time on the project, they asked the course teacher, Dr. Michael Rodeh, for academic credit in an attempt to avoid unnecessary exams. Being the manager of the IBM Research Lab in Haifa and well aware of the overwhelming number of different languages to choose from, he agreed— with the stipulation that they cooperate with the existing developers of PHP/ FI instead of starting their own language.

Created: March 27, 2003
Revised: Sept 1, 2003