I learned C in college classes, but never really learned it until after a "WTF PHP" moment, so I could dig into the interpreter source to figure out what was going on. Later experience with Python's interpreter and debugging pyrex reinforced my knowledge.
I mention this just to say why I think "modern" very-high-level language hackers still end up learning C; the base layer is all written in it, and eventually you've either got to fix something or write something fast.
I find it more than a little disturbing that the first time you really used C was to figure out the PHP interpreter. It's among the worst C code I've ever seen (aside from code I've seen on dailywtf). After I had to debug something in the PHP interpreter, I refused to have anything to do with PHP ever again.
Anyway I hope for your sake looking at the Python interpreter did more than reinforce your knowledge. It's no stroke of genius, but it's much better written than PHP.
I mention this just to say why I think "modern" very-high-level language hackers still end up learning C; the base layer is all written in it, and eventually you've either got to fix something or write something fast.
(I'm 28)