When working with many websites on one development environment using Apache you may run into the issue where one website references a different websites files.  This usually happens if you have a php include path set in your ini file for one site and not the other.  A quick way to keep this from happening is using an htaccess file to set your php include path for each site. (Personally I think this is just an easier way to maintain them)

Either create an .htaccess file or edit an existing one in the website root.  Please note that for my development environment I use vhosts in my apaches config settings so I can call my sites directly by a URL and NOT using localhost.  Therefore I can set an individual include path in each site’s directory.

Here is what you need to add to the htaccess file:

Windows:

php_value include_path "C:/yourpath/mywebsite"

Linux:

php_value include_path "/yourpath/mywebsite"