code: private function writeBreaks(XMLWriter $objWriter, PhpspreadsheetWorksheet $pSheet)
      {
          // Get row and column breaks
          $aRowBreaks = [];
          $aColumnBreaks = [];
          foreach ($pSheet->getBreaks() as $cell => $breakType) {
              if ($breakType == PhpspreadsheetWorksheet::BREAK_ROW) {
                  $aRowBreaks[] = $cell;
              } elseif ($breakType == PhpspreadsheetWorksheet::BREAK_COLUMN) {
                  $aColumnBreaks[] = $cell;
              }
          }
  
          // rowBreaks
          if (!empty($aRowBreaks)) {
              $objWriter->startElement('rowBreaks');
              $objWriter->writeAttribute('count', count($aRowBreaks));
              $objWriter->writeAttribute('manualBreakCount', count($aRowBreaks));
  
              foreach ($aRowBreaks as $cell) {
                  $coords = Coordinate::coordinateFromString($cell);
  
                  $objWriter->startElement('brk');
                  $objWriter->writeAttribute('id', $coords[1]);
                  $objWriter->writeAttribute('man', '1');
                  $objWriter->endElement();
              }
  
              $objWriter->endElement();
          }
  
          // Second, write column breaks
          if (!empty($aColumnBreaks)) {
              $objWriter->startElement('colBreaks');
              $objWriter->writeAttribute('count', count($aColumnBreaks));
              $objWriter->writeAttribute('manualBreakCount', count($aColumnBreaks));
  
              foreach ($aColumnBreaks as $cell) {
                  $coords = Coordinate::coordinateFromString($cell);
  
                  $objWriter->startElement('brk');
                  $objWriter->writeAttribute('id', Coordinate::columnIndexFromString($coords[0]) - 1);
                  $objWriter->writeAttribute('man', '1');
                  $objWriter->endElement();
              }
  
              $objWriter->endElement();
          }
      }
docs: Write Breaks.
  
  @param XMLWriter $objWriter XML Writer
  @param PhpspreadsheetWorksheet $pSheet Worksheet