(PHP 4, PHP 5)
defined — Checks whether a given named constant exists
Checks whether the given constant exists and is defined.
Informacja: 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().
The constant 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;
}
?>