is_subclass_of

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

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

Опис

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.

Параметри

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.

Значення, що повертаються

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

Приклади

Приклад #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";
}
?>

Поданий вище приклад виведе:

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

Приклад #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";
}
?>

Поданий вище приклад виведе:

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

Примітки

Зауваження:
Ця функція буде використовувати будь-який зареєстрований автозавантажувач, якщо клас ще не відомий.

Прогляньте також

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 whether the object is of a given type or subtype
class_parents() - Return the parent classes of the given class

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User Contributed Notes 3 notes

down

gunniboyh at web dot de ¶

18 years ago

is_subclass_of() works also with classes between the class of obj and the superclass.

example:
<?php
class A {};
class B extends A {};
class C extends B {};

$foo=new C();
echo ((is_subclass_of($foo,'A')) ? 'true' : 'false');
?>

echoes 'true' .

down

nicholas at aquarionics dot com ¶

15 years ago

This might be useful to someone, so:

If you're using Autoload, you should be aware that this will attempt to autoload $classname if it isn't already loaded. I discovered this when I had something using is_subclass_of inside an error thrown by autoload, which then recursed until it ran out of memory.

down

alan at jynxy.net ¶

6 years ago

The $allow_string parameter is not very clearly documented. When true, it simply allows the first parameter to be the name of a class, instead of an object whose class we are interested in.

Some usage examples:

class parent_class {
    // objects and methods ...
}

$possible_child_object = new possible_child_class(); // might be an extension of parent_class

$result = is_subclass_of($possible_child_object, 'parent_class'); //  valid
$result = is_subclass_of($possible_child_object, 'parent_class', false); //  valid
$result = is_subclass_of('possible_child_class', 'parent_class', true); // valid
$result = is_subclass_of('possible_child_class', 'parent_class', false); // not valid

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