FCMClient.php
public function createTopicNotification($title = null, $body = null, $topic = null)
    {
        $notification = new TopicNotification();
        $notification
            ->setTitle($title)
            ->setBody($body)
            ->setTopic($topic);

        return $notification;
    }
public function createTopicNotification($title = null, $body = null, $topic = null)
    {
        $notification = new TopicNotification();
        $notification
            ->setTitle($title)
            ->setBody($body)
            ->setTopic($topic);

        return $notification;
    }
public function createTopicNotification ( $ title = null , $ body = null , $ topic = null ) { $ notification = new TopicNotification ( ) ; $ notification -> setTitle ( $ title ) -> setBody ( $ body ) -> setTopic ( $ topic ) ; return $ notification ; }
Create a notification of type Topic

@param null $title
@param null $body
@param null $topic
@return TopicNotification
Create a notification of type Topic