When I send any notification from Firebase console, I can monitor my notification status (how many device received or how many opened it) from Firebase console.
Now I developed a PHP backend and using
For the How many devices are received my notification part, I think you should make use of Delivery Receipts:
Delivery Receipt: If the app server included
delivery_receipt_requestedin the downstream message, the XMPP connection server sends a delivery receipt when it receives confirmation that the device received the message.
For the how many devices opened it part, I think this should be a custom implementation on your client app. For example, if the user does click your notification and open a specific activity of your app, you should then Send an Upstream message, specifying that the notification was opened.