is_callable

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

is_callable — Verify that the contents of a variable can be called as a function

Description

is_callable ( mixed $var [, bool $syntax_only = false [, string &$callable_name ]] ) : bool

Verify that a value is a callable.

Parameters

var

The value to check

syntax_only

If set to true the function only verifies that var 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 var 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

As of PHP 5.3.0 is_callable() reports constructors as not being callable. This affects PHP 5 style constructors (__construct) as well as PHP 4 style constructors (i.e. methods with the same name as the class). Formerly, both cases have been considered 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)

See Also

© 1997–2020 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.is-callable.php