public function Authenticate($uid, $pass)
 {
     $pwd_hash = '';
     $stmt = ulPdoDb::Prepare('auth', 'SELECT password FROM ul_logins WHERE id=?');
     if (!ulPdoDb::BindExec($stmt, array(&$pwd_hash, 'str'), array(&$uid, 'int'))) {
         ul_db_fail();
         return ulLoginBackend::BACKEND_ERROR;
     }
     if (ulPdoDb::Fetch($stmt) == false) {
         return ulLoginBackend::NO_SUCH_USER;
     }
     if (ulPassword::Verify($pass, $pwd_hash)) {
         $this->AuthResult = $uid;
         return true;
     } else {
         $this->AuthResult = false;
         return ulLoginBackend::BAD_CREDENTIALS;
     }
 }