code: protected function normalizePdoRowKeyCase(array $row, $multiple)
      {
          if ($this->db->getSlavePdo()->getAttribute(\PDO::ATTR_CASE) !== \PDO::CASE_UPPER) {
              return $row;
          }
  
          if ($multiple) {
              return array_map(function (array $row) {
                  return array_change_key_case($row, CASE_LOWER);
              }, $row);
          }
  
          return array_change_key_case($row, CASE_LOWER);
      }
docs: Changes row's array key case to lower if PDO's one is set to uppercase.
  @param array $row row's array or an array of row's arrays.
  @param bool $multiple whether multiple rows or a single row passed.
  @return array normalized row or rows.
  @since 2.0.13