Class and Interface share SAME namespace!
class k{}
interface k {} // Fatal error: Cannot redeclare class k
interface_exists
(PHP 5 >= 5.0.2, PHP 7, PHP 8)
interface_exists — Checks if the interface has been defined
Description
Checks if the given interface has been defined.
Return Values
Returns true if the interface given by
interface has been defined, false otherwise.
Examples
Example #1 interface_exists() example
<?php
// Check the interface exists before trying to use it
if (interface_exists('MyInterface')) {
class MyClass implements MyInterface
{
// Methods
}
}
?>See Also
- get_declared_interfaces() - Returns an array of all declared interfaces
- class_implements() - Return the interfaces which are implemented by the given class or interface
- class_exists() - Checks if the class has been defined
- enum_exists() - Checks if the enum has been defined
add a note
User Contributed Notes 4 notes
CoR ¶
8 years ago
andrey at php dot net ¶
20 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.
nils dot rocine at gmail dot com ¶
13 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...
<?php
$foo 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.)
<?php
interface_exists(__NAMESPACE__ . '\MyInterface', false);
?>
maxim at inbox dot ru ¶
12 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
ROOT::THEMES ; ROOT::LOC ; ?> . Much faster then Define, but you cant put algorithms inside, only complite strings / __file__ / etc.
