I encountered a few really good discussions relating to PHP – its pitfalls, caveats, and advantages. Here’s some worthwhile reading if you’re looking for arguments to switch from, stick with, or support PHP:

http://maurus.net/work/php-sucks/
http://www.sitepoint.com/blogs/?p=1429
http://www.tbray.org/ongoing/When/200x/2006/02/17/PHP