defined
(PHP 3, PHP 4, PHP 5)
defined -- Checks whether a given named constant exists
Description
bool
defined ( string name )
Checks whether the given constant exists and is defined.
Return Values
Returns TRUE if the named constant given by name
has been defined, FALSE otherwise.
Examples
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;
}
?>
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