IsSubclassOf

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

( excerpt from http://php.net/manual/en/reflectionclass.issubclassof.php )

public function isSubclassOf(
  mixed $class,
): bool;

Checks if the class is a subclass of a specified class or implements a specified interface.

Parameters

• mixed $class

Returns

• bool - Returns TRUE on success or FALSE on failure.