This section lists standard predefined classes. Miscellaneous extensions define other classes which are described in their reference.
These classes are defined in the standard set of functions included in the PHP build.
These additional predefined classes were introduced in PHP 5.0.0.
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.
Following identifiers may not be used as a class name as they have special purpose.