I am using android gcm to make push notifications for my users. Everything is working so fine. To send a notification I need the users registration id to identify him. It works. Now my problem is that I have some hundreds of users and I would like to inform them ALL about certain updates. Is there a way to send a notification to all users? Do I really have to push them all by their registration ids? On the server side I am using PHP and CURL as it is shown in many examples around here...