FCMClient.php
public function subscribeDevicesToTopic($topicId = null, $deviceTokens = array())
    {
        if(!$topicId || empty($deviceTokens)){
            throw new \InvalidArgumentException("Please check arguments!");
        }

        return $this->client->addTopicSubscription($topicId, $deviceTokens);
    }
public function subscribeDevicesToTopic($topicId = null, $deviceTokens = array())
    {
        if(!$topicId || empty($deviceTokens)){
            throw new \InvalidArgumentException("Please check arguments!");
        }

        return $this->client->addTopicSubscription($topicId, $deviceTokens);
    }
public function subscribeDevicesToTopic ( $ topicId = null , $ deviceTokens = array ( ) ) { if ( ! $ topicId || empty ( $ deviceTokens ) ) { throw new \ InvalidArgumentException ( "Please check arguments!" ) ; } return $ this -> client -> addTopicSubscription ( $ topicId , $ deviceTokens ) ; }
Subscribe devices to a Topic

@param null $topicId
@param array $deviceTokens
@return \Psr\Http\Message\ResponseInterface
Subscribe devices to a Topic