They're not lagging behind. Based on my experience, companies in the bay area using PHP often pay just as competitively as others. There are likely a large number of "PHP" jobs available overall though which could bring average pay down, the low-end is low because there's such a low barrier to entry for something like WordPress development.
> There are likely a large number of "PHP" jobs available overall though which could bring average pay down, the low-end is low because there's such a low barrier to entry for something like WordPress development.
I was about to write exactly that. There is a long tail of relatively unskilled developers who technically count as PHP devs. I also do not perceive PHP salaries to be lower relative to other web dev stacks.
