defined

(PHP 3, PHP 4 >= 4.0.0)

defined -- Checks whether a given named constant exists

Description

bool defined ( string name)

Returns TRUE if the named constant given by name has been defined, FALSE otherwise.

Example 1. Checking Constants <?php if (defined("CONSTANT")){ // Note that it should be quoted echo CONSTANT; // } ?>

See also define(), constant(), get_defined_constants() and the section on Constants.