is_subclass_of

(PHP 4, PHP 5, PHP 7, PHP 8)

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

Description

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

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";
}
?>

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.

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

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