These are things I've found on the Internet. Look upon my works ye mighty and despair.
Catching Elephant is a theme by Andy Taylor
An interface is a fully abstract class; none of its methods are implemented and instead of a class sub-classing from it, it is said to implement that interface.
What is the difference between an Abstract class and an Interface in PHP. A good thing to know before doing a phone interview with Digg ;-)
PHP 5 OOP: Interfaces Abstract Classes and the Adapter Pattern
