Adds an event listener that listens on the specified events.
string|array $events The event(s) to listen on.:
object $listener The listener object.:
public function addEventListener($events, $listener) {
// Picks the hash code related to that listener
$hash = spl_object_hash($listener);
foreach ((array) $events as $event) {
// Overrides listener if a previous one was associated already
// Prevents duplicate listeners on same event (same instance only)
$this->_listeners[$event][$hash] = $listener;
}
}