code: private function writeBIFF8CellRangeAddressFixed($range)
      {
          $explodes = explode(':', $range);
  
          // extract first cell, e.g. 'A1'
          $firstCell = $explodes[0];
  
          // extract last cell, e.g. 'B6'
          if (count($explodes) == 1) {
              $lastCell = $firstCell;
          } else {
              $lastCell = $explodes[1];
          }
  
          $firstCellCoordinates = Coordinate::coordinateFromString($firstCell); // e.g. [0, 1]
          $lastCellCoordinates = Coordinate::coordinateFromString($lastCell); // e.g. [1, 6]
  
          return pack('vvvv', $firstCellCoordinates[1] - 1, $lastCellCoordinates[1] - 1, Coordinate::columnIndexFromString($firstCellCoordinates[0]) - 1, Coordinate::columnIndexFromString($lastCellCoordinates[0]) - 1);
      }
docs: Write a cell range address in BIFF8
  always fixed range
  See section 2.5.14 in OpenOffice.org's Documentation of the Microsoft Excel File Format.
  
  @param string $range E.g. 'A1' or 'A1:B6'
  
  @return string Binary data