PHP Manual: Checks if the object has this class as one of its parents or implements it.

Description

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 or implements it.

Parameters

object: A class name or an object instance. No error is generated if the class does not exist.
class_name: The class name
allow_string: 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.

Changelog

Version	Description
5.3.9	Added `allow_string` parameter
5.3.7	Added support for `class_name` to work with interfaces
5.0.3	You may also specify the `object` parameter as a string (the name of the class)

Examples

Example #1 is_subclass_of example


<?php
// 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";
}


// usable only since PHP 5.0.3
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";
}
?>

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

Example #2 is_subclass_of using interface example


<?php
// Define the Interface
interface MyInterface
{
  public function MyFunction();
}

// Define the class implementation of the interface
class MyClass implements MyInterface
{
  public function MyFunction()
  {
    return "MyClass Implements MyInterface!";
  }
}

// Instantiate the object
$my_object = new MyClass;

// Works since 5.3.7

// Test using the object instance of the class
if (is_subclass_of($my_object, 'MyInterface')) {
  echo "Yes, \$my_object is a subclass of MyInterface\n";
} else {
  echo "No, \$my_object is not a subclass of MyInterface\n";
}

// Test using a string of the class name
if (is_subclass_of('MyClass', 'MyInterface')) {
  echo "Yes, MyClass is a subclass of MyInterface\n";
} else {
  echo "No, MyClass is not a subclass of MyInterface\n";
}
?>

The above example will output:

Yes, $my_object is a subclass of MyInterface
Yes, MyClass is a subclass of MyInterface

Notes

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

is_subclass_of