is_callable

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

is_callable — 检测参数是否为合法的可调用结构

说明

is_callable ( callable $name , bool $syntax_only = false , string &$callable_name = ? ) : bool

验证变量的内容能否作为函数调用。 这可以检查包含有效函数名的变量，或者一个数组，包含了正确编码的对象以及函数名。

参数

name

要检查的回调函数。

syntax_only

如果设置为 true，这个函数仅仅验证 name 可能是函数或方法。 它仅仅拒绝非字符，或者未包含能用于回调函数的有效结构。有效的应该包含两个元素，第一个是一个对象或者字符，第二个元素是个字符。

callable_name

接受"可调用的名称"。下面的例子是"someClass::someMethod"。 注意，尽管 someClass::SomeMethod() 的含义是可调用的静态方法，但例子的情况并不是这样的。

返回值

如果 name 可调用则返回 true，否则返回 false。

范例

Example #1 is_callable() 例子

<?php
//  How to check a variable to see if it can be called
//  as a function.

//
//  Simple variable containing a function
//

function someFunction() 
{
}

$functionVariable = 'someFunction';

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

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

//
//  Array containing a method
//

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

?>

参见

User Contributed Notes

mohamed dot elidrissi at protonmail dot com 28-Jun-2021 12:26
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)

?>
jlh 22-Mar-2019 09:28
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
izharaazmi at gmail dot com 11-Jan-2016 06:50
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
?>
fgm at osinet dot fr 27-Jun-2011 05:03
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
?>
rahadotaboulfethatgmail.com 01-Mar-2008 04:44
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
Quis strrev TA omicidio strrev TOD com 13-Nov-2007 03:50
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