mdb2: how to save a connection in a session

Hi, I have a little problem I don't know if is concerning php (or better my ignorance) or mdb2; I've asked myself but I received no answer so I ask you... I would like to save, in a session variable, a mdb2 connection object but when I try to re-read it I get the error: > Please ensure that the class definition "MDB2_Driver_pgsql" of the object you > are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() > function to load the class definition in ... I have already tried to add a "require_once 'MDB2/Driver/pgsql.php'" without success. What I wrong? There is no way to save a mdb2 connection object in a session variable? Thank you very much Piviul