is_callable

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

&reftitle.description; `bool` `is_callable` `mixed` `value` `bool` `syntax_only`&false; `string` `callable_name`&null;

Verify that a value is a `callable`.

&reftitle.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.

&reftitle.returnvalues;

Returns &true; if `value` is callable, &false; otherwise.

&reftitle.examples;

### `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

    ?>

### `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'))
    );

&example.outputs;

    bool(false)
    bool(false)

&reftitle.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.

&reftitle.seealso;

- `function_exists`
- `method_exists`