defined
Checks whether a given named constant exists
Syntax
defined ( string $name ) : bool
Parameters
name
The constant name.
Return
Returns TRUE if the named constant given by name has been defined, FALSE otherwise.
Examples
1
<?
define("MYCONSTANT", "Hello World!");
$return = defined("MYCONSTANT");
var_export($return);
?>
true
2
<?
$return = defined("MYCONSTANT");
var_export($return);
?>
false