// First try to update an existing row...
   $result = db_query("
      UPDATE {$db_prefix}sessions
      SET data = '" . addslashes($data) . "', last_update = " . time() . "
      WHERE session_id = '" . addslashes($session_id) . "'
      LIMIT 1", __FILE__, __LINE__);

   // If that didn't work, try inserting a new one.
   if (db_affected_rows() == 0)
      $result = db_query("
         INSERT IGNORE INTO {$db_prefix}sessions
            (session_id, data, last_update)
         VALUES ('" . addslashes($session_id) . "', '" . addslashes($data) . "', " . time() . ")", __FILE__, __LINE__);

   return $result;
}