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

    Verifies that value is a callable, or that it can be called using the call_user_func() function.

    Parameters

    value

    The value to be checked.

    syntax_only

    If set to true the function only verifies that value might be a function or method. It will reject any values that are not invokable objects, Closure, strings, or arrays that do not have a valid structure to be used as a callback. A valid callable array has 2 entries, the first of which is an object or a string, and the second a string.

    callable_name

    Receives the "callable name", e.g. "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 Checking whether a string can be called as a function

    <?php

    function someFunction() {}

    $functionVariable = 'someFunction';

    var_dump(is_callable($functionVariable, false, $callable_name));

    var_dump($callable_name);

    ?>

    The above example will output:

    bool(true)
string(12) "someFunction"

    Example #2 Checking whether an array can be called as a function

    <?php

    class SomeClass
    {
    public function     someMethod() {}
    }

    $anObject = new SomeClass();

    $methodVariable = [$anObject, 'someMethod'];

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

    var_dump($callable_name);

    ?>

    The above example will output:

    bool(true)
string(21) "SomeClass::someMethod"

    Example #3 is_callable() and constructors

    Despite the fact that constructors are the methods that are called when an object is created, they are not static methods and is_callable() will return false for them. It's not possible to use is_callable() to check if a class can be instantiated from the current scope.

    <?php

    class Foo
    {
    public function     __construct() {}

    public function     foo() {}
    }

    var_dump(
    is_callable(['Foo', '__construct']),
    is_callable(['Foo', 'foo'])
    );

    $foo = new Foo();
    var_dump(is_callable([$foo, '__construct']));

    ?>

    The above example will output:

    bool(false)
bool(false)
bool(true)

    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

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    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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