defined

(PHP 3, PHP 4 >= 4.0b1)

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() and the section on Constants.