Nope, we don't only talk about Ruby. We have a few PHP examples as well, but there's a lot more on CSS, JS, Git, server administration, etc.

There's not a lot of server-side code in the book, to be honest. Chapters like Creating a Widget focus on the client-side code - loading content in to your page and providing an example for what the data looks like, without getting in to "here's how you'd' do this in Ruby or PHP or .NET".