Active Directory user group login

[ChetUbetcha]

I'd like to bypass making a user administration system on my network website. How do I use PHP to grab the user session from Active Directory and set my website to only allow people from a certain User Group?

Do I have to have certain PHP files (i.e. php.ini) on the server set to anything in particular? I don't have access to make those changes, so I'd have to know what to tell them to do.

Also, do I have to have certain permissions to read information from the Active Directory server? If so, what do I need to ask of my IT office in order to make those changes?

Thanks!

[ChetUbetcha]

I finally got rid of the mental block and remembered the term "LDAP". Duh! Anyway, I'm still looking for a solution and BTW it's a Windows environment.