is_callable

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

is_callable — Verify that a value can be called as a function from the current scope.

Description

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

Verify that a value is a callable.

Parameters

value

The value to check

syntax_only

If set to true the function only verifies that value might be a function or method. It will only reject simple variables that are not strings, or an array that does not have a valid structure to be used as a callback. The valid ones are supposed to have only 2 entries, the first of which is an object or a string, and the second a string.

callable_name

Receives the "callable name". In the example below it is "someClass::someMethod". Note, however, that despite the implication that someClass::SomeMethod() is a callable static method, this is not the case.

Return Values

Returns true if value is callable, false otherwise.

Examples

Example #1 is_callable() example

<?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

?>

Example #2 is_callable() and constructors

is_callable() reports constructors as not being callable.

<?php

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

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

The above example will output:

bool(false)
bool(false)

Notes

  • An object is always callable if it implements __invoke(), and that method is visible in the current scope.
  • A class name is callable if it implements __callStatic().
  • If an object implements __call(), then this function will return true for any method on that object, even if the method is not defined.
  • This function may trigger autoloading if called with the name of a class.

See Also