is_subclass_of

Checks if the object has this class as one of its parents or implements it

Description

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

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

Parameters

object_or_class: A class name or an object instance. No error is generated if the class does not exist.
class: The class name
allow_string: If this parameter set to false, string class name as object_or_class 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_or_class, belongs to a class which is a subclass of class, false otherwise.

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";
}


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";
}
?>