This forum is powered by XenForo, which is a PHP back-end. You can also use a site called "BuiltWith" to look up sites to see what info they expose in regards to server information, backend languages, etc.
Knowing the backend language isn't going to do much for "hacking". Any language can have vulnerabilities - it's the implementation of the language that's important. For example, PayPal and Facebook are both also written in PHP in the back end. Knowing that gives me no "edge" really.