defined
PHP 4, PHP 5, PHP 7, PHP 8
defined - Checks whether a given named constant exists
Manual
defined(
string$constant_name ): bool
Checks whether the given constant exists and is defined.
Note:
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.
Parameters
- constant_name
-
The constant name.
Return Values
Returns true if the named constant given by constant_name has been defined, false otherwise.