Great read, but I think it's a few years too late. When you compare how PHP is trending against languages like Python it's following a similar path as perl, https://www.google.com/trends/explore#q=php%2C%20javascript%... - I'm surprised JavaScript isn't having much of an upturn lately.
Silly me. I forget that not everybody lives in the world of development. Considering this it seems every language is experiencing a downturn. To me this looks more like a fault in Google's trend calculation. Maybe it doesn't consider search inflation from year to year.