In this part 2 of the Google Drive Series, We are going to dig the most important and confusing concept of connecting with Google APIs. Yes, I wrote confusing because there many developers who get confused when they need to implement connectivity of their application to Google APIs. I will try to make this concept easier in this post.
I assume you have read the first part of this series and have created a project in Google Developers Console and before than that have downloaded the PHP Client libraries to play with.