I am developing a Purchase Order system for a manufacturing company in PHP. They are setup on a domain, and I"m wondering if there is a way that I can integrate Active Directory permissions into PHP, does anyone know how I can do this?

I believe this is possible if you access Active Directory via LDAP. Take a look at some of the posts on php.net on the LDAP function reference page.

I just migrated an ASP web app to PHP and ran into this same issue. I will direct you to a great PHP LDAP class that did everything I needed:

Good Luck!

http://adldap.sourceforge.net/