(PHP 5 >= 5.0.2, PHP 7, PHP 8)

interface_existsChecks if the interface has been defined


interface_exists(string $interface, bool $autoload = true): bool

Checks if the given interface has been defined.

Elenco dei parametri


The interface name


Whether to call __autoload or not by default.

Valori restituiti

Returns true if the interface given by interface has been defined, false otherwise.


Example #1 interface_exists() example

// Check the interface exists before trying to use it
if (interface_exists('MyInterface')) {
MyClass implements MyInterface
// Methods


Vedere anche:

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User Contributed Notes 4 notes

andrey at php dot net
18 years ago
As far as I remember interface_exists() was added in 5.0.2 . In 5.0.0 and 5.0.1 class_exists() used to return TRUE when asked for a existing interface. Starting 5.0.2 class_exists() doesn't do that anymore.
7 years ago
Class and Interface share SAME namespace!

class k{}

interface k {}    // Fatal error: Cannot redeclare class k
maxim at inbox dot ru
10 years ago
If you want to check for included interface and you already register spl autoloader - it will crash. Becassue autoloader trying to load `string` and he doesnt matter is it class or not.
Iv found several ways :
1 - unregister AL - -> check for Ifaces - -> register Autoloader

2 - $ifaces = array_flip(get_declared_interfaces());
if($ifaces["MyIface"]) // empty // isset .

Interfaces are not bad, you can build correct geomentry of system , with validation by funcs / vars / const .
Also they are good to storage variables <?php
::THEMES ; ROOT::LOC ; ?> . Much faster then Define, but you cant put algorithms inside, only complite strings / __file__ / etc.
nils dot rocine at gmail dot com
11 years ago
A little note on namespaces that may be obvious to some, but was not obvious to me.

Although you can make the below statement when the statement is in the same namespace as the interface/class declaration MyInterface...
instanceof MyInterface

Making use of the interface_exists, or class_exists functions, you must enter the full namespaced interface name like so (even if the function call is from the same namespace.)
(__NAMESPACE__ . '\MyInterface', false);
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