code: protected function _select($cols, $where = null,
                                  ?array $bind = null,
                                  ?array $order_by = null,
                                  ?array $limit = null, string $return = self::ALL) {
          $query = self::Db()->select($cols)->from($this->_table);
          if (isset($where))
              $query->where($where);
          if (isset($order_by))
              $query->orderByASC($order_by[1], $order_by[0]);
          if (isset($bind))
              $query->bindValues($bind);
          if (isset($limit))
              $query->offset($limit[0])->limit($limit[1]);
          return $query->$return();
      }
docs: MySQL SELECT
  
  @param $cols
  @param mixed $where
  @param array|null $bind
  @param array|null $order_by
  @param array|null $limit
  @param string $return
  @return mixed