A few years ago, I did a few PHP projects and really started to explore PHP4 a lot. I thought it very comparable to ASP but potentially able to do much more with the Pear libraries. I did so much with PHP that I even made to the third interview for a PHP manager role (I lost it to a guy who also knew Java).
I stopped working with this language a long time ago and focused on ASP.net exclusively. I enhoy the .net world a lot, and it looks good on my CV. You can also do a lot more with a lot less code (some .net developer know only the absolute basics of html and javascript). I always thought that keeping up with PHP would dilute my focus. Still, there is a big appeal to PHP. Lots of large sites work with the LAMP infrastructure. You are more likely to find PHP developers contributing to open source projects. It’s cheap to host and you would be more likely to find a young back-bedroom coder using PHP than C#. I’ve been looking at PHP5 and how much more you can do with it. I’m tempted to start another PHP project in my off hours. Either that or getting into Mono. If I replace the Php in LAMP with Asp.net, would that be a LAMA stack? I keep coming back to the same question: what really good sites are actually built on Asp.net?