A function to determine whether one type extends o

问题:

Is there a way in PHP to know if one class inherits another?

class Controller
{
}

class HomeController extends Controller
{
}

class Dummy
{
}

// What I would like to do

    $result = class_extends('HomeController', 'Controller'); /// true
    $result = class_extends('Dummy', 'Controller'); /// false

回答1:

You need to use instanceof.

Note that implements is incorrect. instanceof should be used in both cases (checking whether an object is an inherited class, or whether the object implements an interface).

Example from manual:

<?php
interface MyInterface
{
}

class MyClass implements MyInterface
{
}

$a = new MyClass;

var_dump($a instanceof MyClass);
var_dump($a instanceof MyInterface);
?>

gives:

bool(true)
bool(true)

回答2:

Yes, you can use

if ($foo instanceof ClassName)
    // do stuff...

EDIT: As far as I know, this should even work for interfaces...

回答3:

May I recomment the instanceof operator?

class A { }
class B extends A { }
class C { }

$b = new B;
$c = new C;

var_dump($b instanceof A, $c instanceof A) // bool(true), bool(false)