public function attach(ObserverInterface $observer)
	{
		if ($this->isAttached($observer)) {
			return false;
		}

		$this->observers[] = $observer;

		return true;
	}
public function attach(ObserverInterface $observer)
	{
		if ($this->isAttached($observer)) {
			return false;
		}

		$this->observers[] = $observer;

		return true;
	}
public function attach ( ObserverInterface $ observer ) { if ( $ this -> isAttached ( $ observer ) ) { return false ; } $ this -> observers [ ] = $ observer ; return true ; }
Returns true if the observer is attached successfully.

@param ObserverInterface $observer
@return bool true if the observer is attached successfully.
Returns true if the observer is attached successfully .