Generally I'm doing side projects to fix an actual need of mine, rather than where some people are trying to learn a new language or framework, so I pick PHP because it's the language that I'm most proficient at, it's probably not the best language for my needs, however the most powerful language is the one that you know!

Are you looking to build something, in which case playing around with new frameworks may just be a distraction...? Or do you actually want to play around with something new?