code: private function writeGridset()
      {
          $record = 0x0082; // Record identifier
          $length = 0x0002; // Bytes to follow
  
          $fGridSet = !$this->phpSheet->getPrintGridlines(); // Boolean flag
  
          $header = pack('vv', $record, $length);
          $data = pack('v', $fGridSet);
          $this->append($header . $data);
      }
docs: Write the GRIDSET BIFF record. Must be used in conjunction with the
  PRINTGRIDLINES record.