Using OAuth2 for Google APIs with PHP

I've been working on something recently where I'm pulling information from lots of places onto a dashboard. Each API has its own little quirks so I'm trying to write up the ones that weren't idiot-proof, mostly so I can refer back to them later when I need to maintain my system!

I've written about Google and OAuth before, but that was OAuth v1.0, and they are introducing OAuth2 for their newer APIs; in this example I was identifying myself in order to use the Google Plus API (which turns out not to do anything you'd expect it to do, but that's a whole separate blog post!). Continue reading