This presentation covers the technical history of PHP, from PHP/FI 2.0 to PHP 4.0, and explores PHP 4.0's design. Gutman and Saraski analyze how the Zend Engine works, targeting points of interest to extension developers. The session explores how to add functionality to PHP, ranging from simple new functions to new extensions. It covers advanced PHP 4.0 features such as resource management and object-oriented syntax overloading.

One of the most important factors of PHP's widespread success is its strong extensibility features. The abstracted module interface introduced in PHP 3.0, succeeded by the even more mature extension API of PHP 4.0's Zend Engine, gives developers a strong and easy to use infrastructure for building new PHP extensions.