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 /* Note the use of quotes, this is important. This example is checking * if the string 'CONSTANT' is the name of a constant named CONSTANT */ if (defined('CONSTANT')) { echo CONSTANT; } ?>
Note:
If you want to see if a variable exists, use
isset() as defined() only
applies to constants.
If you want to see if a function exists, use
function_exists().
