What language is used most for backend?

A survey of W3Techs claims that PHP is the most used backend language. Around 79.2% of web applications are using PHP as server-side applications.

The app is most likely written primarily in Java .

Reddit was written in Lisp, but we rewrote it and now it’s written in Python . We use the Pylons framework, and you can see our source code if you want.

Reddit uses Python as backend language.