Update: GCM is deprecated, use FCM
How can I integrate the new Google Cloud Messaging in a PHP backend?
After searching for a long time finally I am able to figure out what I exactly needed, Connecting to the GCM using PHP as a server side scripting language, The following tutorial will give us a clear idea of how to setup everything we need to get started with GCM
Android Push Notifications using Google Cloud Messaging (GCM), PHP and MySQL