In the PHP 3.0 SDK there is no getSession() or any session handling from outside the Facebook api available. Some days ago the developers of facebook have also
getSession()
Hi i've run in the same trouble seems i've solved it with watching the JS API and redirect to the PHP-SDK Login Page if User Information is readable
example:
if the script succed it loads the loginpage, and user got recognized by both JS and PHP SDK ;)