code: private function writePrintGridlines()
      {
          $record = 0x002b; // Record identifier
          $length = 0x0002; // Bytes to follow
  
          $fPrintGrid = $this->phpSheet->getPrintGridlines() ? 1 : 0; // Boolean flag
  
          $header = pack('vv', $record, $length);
          $data = pack('v', $fPrintGrid);
          $this->append($header . $data);
      }
docs: Write the PRINTGRIDLINES BIFF record. Must be used in conjunction with the
  GRIDSET record.