Interesting but not sure if it is what I want

[ugintl]

I use drupal CMS to create websites. If you do not know drupal, it is quiet similar to wordpress in terms of server requirements. Drupal also allows to integrate 3rd party api.

What I want?

I want something free open source thing which can send messages or notifications (probably push notifications) from my website to users' mobile phones. The user might or might not have our app installed. In fact, I do not have any mobile app currently.

May be you can suggest something else. Actually, I want to try all possibilities to avoid relying on external services. There is a Drupal module which allows to send push notifications, but it relies on GCM and APN. I want to avoid this dependency.

[hhxsv5]

This requires a client, whether it is GCM, APN, or your app.

[ugintl]

If I have an app, can I use phpsse to send messages or notifications to the app?

How?

[hhxsv5]

Sure, you need to make sure your app is open in the foreground/background, and this notification is not system level but application level.

If you have high performance requirements, you can use WebSocket, such as Swoole WebSocket Server.

[lbfalvy]

Push notifications also use HTTP, and thus work quite well with PHP. Don't make a mobile app just to use them.

[hhxsv5]

Now there is already a high performance coroutine SSE Server based on Swoole, enjoy the demo.