These constants are defined by the PHP core. This includes PHP, the Zend engine, and SAPI modules.
Available since PHP 4.3.10 and PHP 5.0.2
Available since PHP 4.4.0 and PHP 5.0.5
Available since PHP 4.4.0 and PHP 5.0.5
Available since PHP 5.0.0
Available since PHP 5.1.0
See also: Magic constants.
These constants are defined in PHP by default.