is_subclass_of()

is_subclass_of() — Checks if the object has this class as one of its parents or implements it.

Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

Checks if the given object_or_class has the class class as one of its parents or implements it.

Signature

is_subclass_of(mixed $object_or_class, string $class, bool $allow_string = true): bool

Parameters

Parameter	Type	What it takes
$object_or_class	mixed	A class name or an object instance. No error is generated if the class does not exist.
$class	string	The class name
$allow_string	bool	If this parameter is set to false, a string class name as object_or_class is not allowed. This also prevents calling the autoloader if the class doesn't exist.

Return value

This function returns true if the object object_or_class, belongs to a class which is a subclass of class, false otherwise.

Example

A runnable snippet:

// define a class class WidgetFactory { var $oink = 'moo'; } // define a child class class WidgetFactory_Child extends WidgetFactory { var $oink = 'oink'; } // create a new object $WF = new WidgetFactory(); $WFC = new WidgetFactory_Child(); if (is_subclass_of($WFC, 'WidgetFactory')) { echo "yes, \$WFC is a subclass of WidgetFactory\n"; } else { echo "no, \$WFC is not a subclass of WidgetFactory\n"; } if (is_subclass_of($WF, 'WidgetFactory')) { echo "yes, \$WF is a subclass of WidgetFactory\n"; } else { echo "no, \$WF is not a subclass of WidgetFactory\n"; } if (is_subclass_of('WidgetFactory_Child', 'WidgetFactory')) { echo "yes, WidgetFactory_Child is a subclass of WidgetFactory\n"; } else { echo "no, WidgetFactory_Child is not a subclass of WidgetFactory\n"; }

Output:

yes, $WFC is a subclass of WidgetFactory no, $WF is not a subclass of WidgetFactory yes, WidgetFactory_Child is a subclass of WidgetFactory