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

add a note

User Contributed Notes 2 notes

up
35
izharaazmi at gmail dot com
8 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
?>
up
19
mohamed dot elidrissi at protonmail dot com
3 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)

?>
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