I do know PHP. A few years back I wrote an online, text-based fighting game in it (called the Octagon), and I have written several small-business websites with it so I know how powerful it can be.
When I do corporate work, though, they all want .NET so I have been concentrating on those skills in the last couple of years. Because of that, I have fallen in love with Visual Studio as an IDE.
Once you can put breakpoints and walk through your code in a webpage, <?="write this"?> just isn't the same.
That being said, if a client wanted PHP, then I wouldn't have a problem writing in it (although I am a bit rusty).
David