Firebase Cloud Messaging PHP Client
composer require ...
$firebase = new FirebaseMessaging('PROJECT_ID', 'YOUR_SERVER_KEY', 'OPTIONAL_API_URL');
$firebase->sendMessageToFcmToken('FCM_TOKEN', 'TITLE', 'BODY');
Can also be array of tokens
$firebase->sendMessageToTopic('TOPIC', 'TITLE', 'BODY');
Can also be array of topics
$firebase->subscribeToTopic('FCM_TOKEN', 'TOPIC');
Can also be array of tokens
$firebase->unsubscribeFromTopic('FCM_TOKEN', 'TOPIC');
Can also be array of tokens