I'm purely ASP at the moment but I have played with PHP. If you are doing PHP, I'd advise sticking with it. I've picked up a book on PHP and have been learning it. Just really learning the structure and how it works. I'm only a few chapters in and I can already see how much better it is. Although I can do most things in ASP, I'm going to try and make the move over to PHP. The language just seems more geared towards developers: easier code, shortcuts, ready components, etc.
As a matter of interest, how long do you think it would take to convert from ASP to PHP in terms of getting to a comfortable real time production skill level?