List of Reserved Words
PHP Manual

Predefined Classes

This section lists standard predefined classes. Miscellaneous extensions define other classes which are described in their reference.

Standard Defined Classes

These classes are defined in the standard set of functions included in the PHP build.

Directory
Created by dir().
stdClass
Created by typecasting to object.
__PHP_Incomplete_Class
Possibly created by unserialize().

Predefined classes as of PHP 5

These additional predefined classes were introduced in PHP 5.0.0.

Exception
php_user_filter

Closure

The predefined final class Closure was introduced in PHP 5.3.0. It is used for representing anonymous functions.

For more information, see its class page.

Special classes

Following identifiers may not be used as a class name as they have special purpose.

self
Current class.
static
Current class in runtime.
parent
Parent class.

List of Reserved Words
PHP Manual