You need a web server set up
It pretty easy to set up webservers on localhost and php you may aswell
install a db too
here are some links
http://www.phpied.com/installing-php-and-apache-on-mac-osx-that-was-pretty-easy/
http://www.sebastiansulinski.co.uk/web_design_tutorials/web_server/installing_
Basic Mod Rewrite's work fin but more complex one crash httpd. Wordpress &
cakePHP when using mod rewrite
I have php4 set up on another instance of apache but can't get php5 to work
with apache
from my error log
[Wed May 02 15:47:51 2007] [notice] Parent: child process exited with status
107380