Calling closure assigned to object property directly

Question

I would like to be able to call a closure that I assign to an object\'s property directly without reassigning the closure to a variable and then calling it. Is this possible

Answer 1

I note that this works in PHP5.5

$a = array();
$a['callback'] = function() {
    print "HelloWorld!";
};
$a['callback']();

Allows one to create a psuedo-object collection of closures.

Answer 2

You can do this by calling __invoke on the closure, since that's the magic method that objects use to behave like functions:

$obj = new stdClass();
$obj->callback = function() {
    print "HelloWorld!";
};
$obj->callback->__invoke();

Of course that won't work if the callback is an array or a string (which can also be valid callbacks in PHP) - just for closures and other objects with __invoke behavior.

Answer 3

well, it should be emphisized that storing the closure in a variable, and call the varible is actually (wierdly) faster, depending on the call amount, it becomes quite a lot, with xdebug (so very precise measuring), we are talking about 1,5 (the factor, by using a varible, instead of directly calling the __invoke. so instead , just store the closure in a varible and call it.

Answer 4

Updated:

$obj = new stdClass();
$obj->callback = function() {
     print "HelloWorld!";
};

PHP >= 7 :

($obj->callback)();

PHP >= 5.4 :

$callback = $obj->callback;  
$callback();

Answer 5

It seems to be possible using call_user_func().

call_user_func($obj->callback);

not elegant, though.... What @Gordon says is probably the only way to go.

Answer 6

Since PHP 7 a closure can be called using the call() method:

$obj->callback->call($obj);

Since PHP 7 is possible to execute operations on arbitrary (...) expressions too (as explained by Korikulum):

($obj->callback)();

Other common PHP 5 approaches are:

• using the magic method __invoke() (as explained by Brilliand)

  $obj->callback->__invoke();
  

• using the call_user_func() function

  call_user_func($obj->callback);
  

• using an intermediate variable in an expression

  ($_ = $obj->callback) && $_();
  

Each way has its own pros and cons, but the most radical and definitive solution still remains the one presented by Gordon.

class stdKlass
{
    public function __call($method, $arguments)
    {
        // is_callable([$this, $method])
        //   returns always true when __call() is defined.

        // is_callable($this->$method)
        //   triggers a "PHP Notice: Undefined property" in case of missing property.

        if (isset($this->$method) && is_callable($this->$method)) {
            return call_user_func($this->$method, ...$arguments);
        }

        // throw exception
    }
}

$obj = new stdKlass();
$obj->callback = function() { print "HelloWorld!"; };
$obj->callback();