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