The Standard PHP Library

The goal of the Standard PHP Library-or SPL, for short-is to provide a standard library of interfaces that allows developers to take full advantage of object-oriented programming in PHP 5. This library of interfaces creates a standard API for certain kinds of built-in functionality, allowing your classes to interact with the PHP engine in a much more seamless manner.

Link:
http://.../2565-The-Standard-PHP-Library-SPL