I have adopted all of the lessons and uncommented the appropriate lines in httpd.conf, but PHP files don't render under Web Discussing.

The server just delivers the origin code rather than running it.

I understand that PHP works, because I'm able to run it completely from the Terminal while using "php" command.

What's happening here?

If put forth system preferences and visit Discussing - is Web Discussing enabled?

Once you transformed the /etc/apache2/httpd.conf file, have you restart Apache?

Try mamp (Mac Apache Mysql PHP). http://www.mamp.info It really works brilliant under Snow Leopard 10.6.4