So what's considered the cool stack right now? Being a PHP developer who built my own web app, NannyLogic, that's making money and love it, but also being fairl

So what's considered the cool stack right now? Being a PHP developer who built my own web app, NannyLogic, that's making money and love it, but also being fairly new to programming, I'm not really aware of what is or isn't cool in hacker circles but I'd be interested to learn new things.