For a few months in 2004 I did a brief stint as a PHP developer. It's on a few older versions of my CV, which has been thoroughly crawled by recruitment agents. Since then I have regularly received speculative emails from recruiters trying to fill PHP developer positions, sometimes as many as 20 a week.

They all pay a lot less than I could earn elsewhere, so I ignore them, but there is definitely massive industry demand for low-mid level PHP developers, at least in the UK. I suspect this might be something to do with how PHP requires a whole bunch of orbital skills before you can really be effective with it, and if you have those skills, you can probably do something more useful with them than code in PHP.