I'd strongly recommend using what you know best. If you're good at PHP, use that. If, however, it's been a long 6 years and you're going to be pretty rusty at

I'd strongly recommend using what you know best. If you're good at PHP, use that. If, however, it's been a long 6 years and you're going to be pretty rusty at whatever you use, I'd recommend giving Node.js a shot. We've had really good luck with it and it has a fantastic community behind it.