(PHP 4, PHP 5)

is_subclass_ofChecks if the object has this class as one of its parents


bool is_subclass_of ( mixed $object , string $class_name [, bool $allow_string = TRUE ] )

Checks if the given object has the class class_name as one of its parents.



A class name or an object instance


The class name


If this parameter set to false, string class name as object is not allowed. This also prevents from calling autoloader if the class doesn't exist.

Return Values

This function returns TRUE if the object object, belongs to a class which is a subclass of class_name, FALSE otherwise.


Version Description
5.3.9 Added allow_string parameter
5.0.3 You may also specify the object parameter as a string (the name of the class)


Example #1 is_subclass_of() example

// define a class
class WidgetFactory
$oink 'moo';

// define a child class
class WidgetFactory_Child extends WidgetFactory
$oink 'oink';

// create a new object
$WF = new WidgetFactory();
$WFC = new WidgetFactory_Child();

if (
is_subclass_of($WFC'WidgetFactory')) {
"yes, \$WFC is a subclass of WidgetFactory\n";
} else {
"no, \$WFC is not a subclass of WidgetFactory\n";

if (
is_subclass_of($WF'WidgetFactory')) {
"yes, \$WF is a subclass of WidgetFactory\n";
} else {
"no, \$WF is not a subclass of WidgetFactory\n";

// usable only since PHP 5.0.3
if (is_subclass_of('WidgetFactory_Child''WidgetFactory')) {
"yes, WidgetFactory_Child is a subclass of WidgetFactory\n";
} else {
"no, WidgetFactory_Child is not a subclass of WidgetFactory\n";

The above example will output:

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



Using this function will use any registered autoloaders if the class is not already known.

See Also

  • get_class() - Returns the name of the class of an object
  • get_parent_class() - Retrieves the parent class name for object or class
  • is_a() - Checks if the object is of this class or has this class as one of its parents
  • class_parents() - Return the parent classes of the given class