src/event/EventManager.php
public function attach(\SplObserver $observer, $eventName = Null, $function = Null, $order = Null) {
        $newEventAttach = new \stdClass();
        $newEventAttach->observer  = $observer;
        $newEventAttach->function  = $function;
        $newEventAttach->eventName = $eventName;
        $newEventAttach->order     = $order;
        $this->_observers->attach($newEventAttach);
    }
public function attach(\SplObserver $observer, $eventName = Null, $function = Null, $order = Null) {
        $newEventAttach = new \stdClass();
        $newEventAttach->observer  = $observer;
        $newEventAttach->function  = $function;
        $newEventAttach->eventName = $eventName;
        $newEventAttach->order     = $order;
        $this->_observers->attach($newEventAttach);
    }
Add new observer to the list

@param \SplObserver        $observer
@param string|null         $eventName
@param string|null         $function
@param mixed |null         $order