public function getListener($event)
    {
        if (!is_string($event) || empty($event)) {
            throw new \InvalidArgumentException('The event name is invalid');
        }

        return $this->listeners[$event];
    }
public function getListener($event)
    {
        if (!is_string($event) || empty($event)) {
            throw new \InvalidArgumentException('The event name is invalid');
        }

        return $this->listeners[$event];
    }
public function getListener ( $ event ) { if ( ! is_string ( $ event ) || empty ( $ event ) ) { throw new \ InvalidArgumentException ( 'The event name is invalid' ) ; } return $ this -> listeners [ $ event ] ; }
Gets the listener assigned to the given event.

@param string $event The name of the event
@return callable
@throws \InvalidArgumentException if the event name is invalid.
Gets the listener assigned to the given event .