A couple people I know well spent the summer there (I actually visited one at the old headquarters; it was pretty cool). One now works there full time (the other hasn't graduated yet). I also talked to some fulltime engineers who were not using PHP.

Now, it's reasonable that I did not get the full picture, but the people I did talk did not use PHP themselves and claimed that new projects didn't either. Perhaps this varies per team. My impression was that existing code bases using PHP were still under active development (that is, getting new features) but new projects and new developers did not use PHP.