Authenticate via HTTP Auth Digest against another System with PHP

Hi, I´m just trying to write a little tool in php which is supposed to edit an LDAP Adressbook for our companys Voice over IP Phones. To get access to the LDAP DB I want to authenticate the User via my PHP Script against the pbx (a black box) which has all user and PW information. Via Browser and HTTP Get I have to authenticate with HTTP Digest to this system. this would mean that the Username/Password combination exist on the system and that is what I want to know... I´ve been looking around for some time searching for PHP functions oder classes to do that but I just found several tutorials on how to implement digest towards my clients of my script. In my case I am the client system... Any ideas on how to solve this problem Thanks in advance Michael