Push Notification using GCM

To create a Google API project:

1. Open the Google Developers Console. https://console.developers.google.com/project
2. Create Project.
3. Copy down your project number. You will use it later on as the GCM sender ID.
4. In the sidebar on the left, select APIs & auth
5. In the displayed list of APIs, turn the Google Cloud Messaging for Android toggle to ON.

To obtain an API key:

1. In the sidebar on the left, select APIs & auth > Credentials.
2. Under Public API access, click Create new key.
3. In the Create a new key dialog, click Server key.
4. Click Create.
5. Give this Server key in your server code.

Android Code :

http://developer.android.com/google/gcm/client.html

http://www.androidhive.info/2012/10/android-push-notifications-using-google-cloud-messaging-gcm-php-and-mysql/