I'm trying to do my own custom dashboard and I want to display some reports from Google Analytics. I've been exploring Google API PHP Client I'm already able to do authentication and some queries. This is nice, but not quite enough: now, I want to display the data retrieved in the form of charts. That lead me to explore Google Solutions section and I stumbled upon Google Analytics Data and Chart Tools. Google provides an example here
However, I can't understand how this works. For example, the html file has a button for authentication, but it doesn't do anything. I'm very confused. I can't understand the authentication proccess via javascript. Can someone help me out?