mcavic - 11:57 pm on Sep 12, 2009 (gmt 0)

Yes, if they're called with an include or require statement, you can put them anywhere. /var/www/classes or /var/www/lib sounds fine if you want them to be accessible system-wide.

Personally, I would then install each site somewhere outside /var/www, like /home/sitename. I create a separate user account for each site, so that it has a directory under home. But it's just a preference, I can't say that's mandatory.