// Instantiate the client with the project api_token and sender_id.
$client = new \Fcm\FcmClient($apiToken, $senderId);

// Instantiate the push notification request object.
$notification = new \Fcm\Push\Notification();

// Enhance the notification object with our custom options.
$notification
    ->addRecipient($deviceId)
    ->setTitle('Hello from php-fcm!')
    ->setBody('Notification body')
    ->setSound('custom_sound')
    ->addData('key', 'value');

// Send the notification to the Firebase servers for further handling.
$client->send($notification);