interface_exists

(PHP 5 >= 5.0.2)

interface_exists — 检查接口是否已被定义

说明

bool interface_exists ( string $interface_name [, bool $autoload ] )

本函数在由 interface_name 给出的接口已定义时返回 TRUE，否则返回 FALSE。

Example #1 interface_exists() 例子


<?php
// Check the interface exists before trying to use it
if (interface_exists('MyInterface')) {
    class MyClass implements MyInterface
    {
        // Methods
    }
}
?>

interface_exists() 默认会尝试调用 __autoload，如果不希望 interface_exists() 去调用 __autoload，可以将 autoload 参数设为 FALSE。

参见 class_exists()。

参数

interface_name: The interface name
autoload: Whether to call __autoload or not by default.

返回值

Returns TRUE if the interface given by interface_name has been defined, FALSE otherwise.

范例

Example #2 interface_exists() example


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

?>

参见

class_exists() - 检查类是否已定义

add a note User Contributed Notes interface_exists

nils dot rocine at gmail dot com 26-Oct-2011 06:35


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);


?>

andrey at php dot net 24-Oct-2004 04:40


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.

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