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is_callable

(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)

is_callable — 验证值是否可以在当前范围内作为函数调用。

说明

is_callable(mixed $value, bool $syntax_only = false, string &$callable_name = null): bool

验证值是 callable。

参数

value: 要验证的值
syntax_only: 如果设置为 true，则函数仅验证 value 可能是函数或方法。它仅拒绝不是字符串的简单变量，或者不能用作回调的有效结构的数组。只有 2 个条目有效，一个是对象或者字符串，其次是字符串。
callable_name: 接受“可调用的名称”。下面的例子是“someClass::someMethod”。注意，尽管 someClass::SomeMethod() 暗示是可调用的静态方法，但事实并非如此。

返回值

如果 value 可调用则返回 true，否则返回 false。

示例

示例 #1 is_callable() 例子

<?php
//  如何检测变量以查看是否可以作为函数调用。

//
//  包含函数的简单变量
//

function someFunction() 
{
}

$functionVariable = 'someFunction';

var_dump(is_callable($functionVariable, false, $callable_name));  // bool(true)

echo $callable_name, "\n";  // someFunction

//
//  包含方法的数组
//

class someClass {

  function someMethod() 
  {
  }

}

$anObject = new someClass();

$methodVariable = array($anObject, 'someMethod');

var_dump(is_callable($methodVariable, true, $callable_name));  //  bool(true)

echo $callable_name, "\n";  //  someClass::someMethod

?>

示例 #2 is_callable() 和构造函数

is_callable() 报告构造函数不可调用。

<?php

class Foo
{
    public function __construct() {}
    public function foo() {}
}

var_dump(
    is_callable(array('Foo', '__construct')),
    is_callable(array('Foo', 'foo'))
);

以上示例会输出：

 
bool(false)
bool(false)

注释

如果对象实现了 __invoke() 且该方法在当前作用域可见，则始终可调用。
如果类名实现了 __callStatic()，则可调用。
如果对象实现 __call()，则此函数对该对象的任何方法将返回 true，即使该方法没有定义。
如果使用类名调用此函数，则会触发自动加载。

参见

function_exists() - 如果给定的函数已经被定义就返回 true
method_exists() - 检查类的方法是否存在

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User Contributed Notes 7 notes

down

izharaazmi at gmail dot com ¶

7 years ago

If the target class has __call() magic function implemented, then is_callable will ALWAYS return TRUE for whatever method you call it.
is_callable does not evaluate your internal logic inside __call() implementation (and this is for good).
Therefore every method name is callable for such classes.

Hence it is WRONG to say (as someone said):
...is_callable will correctly determine the existence of methods made with __call...

Example:
<?php
class TestCallable
{
    public function testing()
    {
          return "I am called.";
    }

    public function __call($name, $args)
    {
        if($name == 'testingOther') 
        {
                return call_user_func_array(array($this, 'testing'), $args);
        }
    }
}

$t = new TestCallable();
echo $t->testing();      // Output: I am called.
echo $t->testingOther(); // Output: I am called.
echo $t->working();      // Output: (null)

echo is_callable(array($t, 'testing'));       // Output: TRUE
echo is_callable(array($t, 'testingOther'));  // Output: TRUE
echo is_callable(array($t, 'working'));       // Output: TRUE, expected: FALSE
?>

down

mohamed dot elidrissi at protonmail dot com ¶

2 years ago

Note that -- as mentioned in the migration guide-- starting from PHP 8.0, is_callable() will not work with non-static methods if you use a class name, instead an object of the class should be provided:

<?php

class Test
{
    public function method1() { }
    public static function method2() { }
}

// Pre PHP 8
var_dump(is_callable(array('Test', 'method1'))); // bool(true)
var_dump(is_callable(array('Test', 'method2'))); // bool(true)

// Post PHP 8
var_dump(is_callable(array('Test', 'method1'))); // bool(false)
var_dump(is_callable(array('Test', 'method2'))); // bool(true)
var_dump(is_callable(array(new Test, 'method1'))); // bool(true)

?>

down

jlh ¶

4 years ago

The story about __call() is a bit more complicated unfortunately. It will always return true ONLY if you pass an instance of a class, not if you pass the class name itself:

<?php
class MyClass {
    public function method() { }
    public function __call($name, $arguments) { }
}

is_callable([MyClass::class, 'method']); // true
is_callable([new MyClass(), 'method']); // true
is_callable([MyClass::class, 'other']); // false!!!
is_callable([new MyClass(), 'other'])); // true

down

rahadotaboulfethatgmail.com ¶

15 years ago

is_callable generates an [E_STRICT] error if the  tested method cannot be called staticly. (and returns the good value)

I used @is_called 
i'm using php 5.2.1

down

Quis strrev TA omicidio strrev TOD com ¶

16 years ago

is_callable() does _not_ check wheter this function is disabled by php.ini's disable_functions

use:

<?PHP
function is_disabled($function) {
  $disabled_functions=explode(',',ini_get('disable_functions'));
  return in_array($function, $disabled_functions);
}
?>

I`m running PHP 5.2.4

down

php dot net at scare dot ca ¶

1 year ago

Note that is_callable('_') will return true, since there is a built-in function called "_". It is an alias for gettext().

/manual/en/function.gettext.php

Searching this site for a function named "_" does not return a result, but it's the first result in a search for "_()".

down

-2

fgm at osinet dot fr ¶

12 years ago

Note that, for the purpose of this function, an abstract method, although necessarily non-callable since it does not have a body, is still considered to be callable:

<?php
abstract class Foo { 
  abstract function bar(); 
}

echo is_callable(array('Foo', 'bar'));
// display: 1
?>

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