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

- « is_bool

- is_countable »

- PHP Manual
- Variable handling Functions
- Verify that a value can be called as a function from the current scope

# 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

- call_user_func() - Call the callback given by the first parameter
- function_exists() - Return true if the given function has been defined
- method_exists() - Checks if the class method exists