static function passinggreen_db()
 {
     if (DatabaseFactory::$passinggreen_db_instance == null) {
         $write = DatabaseFactory::get_db_settings("com/passinggreen/cfg_write");
         $read = DatabaseFactory::get_db_settings("com/passinggreen/cfg_read");
         DatabaseFactory::$passinggreen_db_instance = new Database($read, $write);
     }
     return DatabaseFactory::$passinggreen_db_instance;
 }