Sending notifications to Google Cloud Messaging with php gives me Unauthorized Error 401

Question

Searching for some info about how to send notifications using GCM but with PHP instead of servlets, i found this: GCM with PHP (Google Cloud Messaging)

I tested the

Answer 1

You need to use the key for server apps in the field of API key in your server side coding. While creating the server key don't enter anything inside IP address field.