Ask HN: Whats the most popular web scripting language?

A recent discussion with one of my coworkers inspired me to do some research about what is the most used language for building web sites. My claim was that there are more web sites out there right now written in PHP than any other single language. I haven't been able to find any evidence or comparisons on just programming languages and the web though.

Does anyone have any good links to research? Does anyone know the answer? I have $1 riding on PHP and I'm looking to collect!