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;
}
?>
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See also define(),
constant(),
get_defined_constants(),
function_exists(), and the section on
Constants.
