19.1. Introduction

PHP, or PHP: Hypertext Preprocessor, has become the most popular server-side scripting language for creating dynamic web pages. PHP was created by Rasmus Lerdorf to track users at his website. In 1995, Lerdorf released it as a package called the “Personal Home Page Tools.” Two years later, PHP 2 featured built-in database support and form handling. In 1997, PHP 3 was released after a substantial rewrite, which resulted in a large increase in performance and led to an explosion of PHP use. The release of PHP 4 featured the new Zend Engine from Zend, a PHP software company. This version was considerably faster and more powerful than its predecessor, further increasing PHP’s popularity. It’s estimated that over 15 million domains now use PHP, accounting for more than 20 percent of web pages.¹ Currently, PHP 5 features the Zend Engine 2, which provides further speed increases, exception handling and a new object-oriented programming model.² More information about the Zend Engine can be found at www.zend.com.