I

implements

The keyword that replaces extends when inheriting an interface rather than a class

inheritance

The ability of an OO language to pass the methods and data members of an existing class on to a new class

instance

A specific occurrence of a class; creation of a class object is referred to as instantiation

interface

1. A keyword in PHP indicating a class that declares methods but does not define them. PHP allows multiple interfaces to be inherited. 2. The public methods of a class.

Iterator

An interface, built in to PHP 5, that allows objects to be traversed