The author's biggest mistake wasn't betting on PHP, it was betting on a single language. He should have learned more languages a long time ago, just to expand his set of tools, and maybe way of thinking.
Besides, learning a new language is fun and not that hard... They are all pretty much the same...
I think it's important to also show the graph of absolute numbers of computer science students. Maybe the absolute numbers will show that the number of female students did not decrease, but rather the numner of male students increased dramatically, making the female share drop.
thanks for your valuable tl;dr.
if Seinfeld would have been a blog post in 2015, HN would summarize:
tl:dr nothing important, kinda funny, but I like Frasier