single sign on Solution php and .net

Hi, me and my fellow developer have built two applications that need to authenticate users using LDAP, we have successfully accomplished it, but the problem is his application is in .net and mine is in php, my php app needs to call secure pages of .net and vice versa, now when the user is logged onto let say my php app he is logged and his session is created and when I redirect him to .net app he again sees a login form because the session isnt created in .net app. I need some single sign on solution I found lots of APIs and libraries for java but have no idea what can I use for php and .net, kindly experience programmers guide me. Thankyou -- Murtaza Chang http://flickr.com/photos/blackstallion/