Android Question Automatic Notifications

You mean you want to send notifications from your server, which is using PHP/MySQL, to all your app users? Are you using the GCM notifications in your app?

If you're wanting to do things server-side, then the simplest way would be to set up a cron job to run every two hours on the server.

There's example code on the forum about how to set up GCM notifications in your app; you have to register it with Google's services to do that. When the app runs, it registers with GCM, and gets an id. It should then pass that ID to your website, which will use it to send notifications - for example, by storing the id in a database and then running through all those IDs in turn, every two hours.

Of course, that pre-supposes you want to send the notification from your web site, and it may be different each time. If you simply want your app to do something every two hours, you could use a service to create the notifications, and call StartServiceAt to schedule a new invocation in two hours time.