public function extend($id, callable $callback)
    {
        if (is_callable($callback) || method_exists($callback, '__invoke')) {
            $this->callables[$id] = $callback;
        }
    }
public function extend($id, callable $callback)
    {
        if (is_callable($callback) || method_exists($callback, '__invoke')) {
            $this->callables[$id] = $callback;
        }
    }
public function extend ( $ id , callable $ callback ) { if ( is_callable ( $ callback ) || method_exists ( $ callback , '__invoke' ) ) { $ this -> callables [ $ id ] = $ callback ; } }
Binds the callable function and executes it by its id

@param string   $id       The callable function id
@param callable $callback The callable function
Binds the callable function and executes it by its id