code: private function createNewCell($pCoordinate)
      {
          $cell = new Cell(null, DataType::TYPE_NULL, $this);
          $this->cellCollection->add($pCoordinate, $cell);
          $this->cellCollectionIsSorted = false;
  
          // Coordinates
          $aCoordinates = Coordinate::coordinateFromString($pCoordinate);
          if (Coordinate::columnIndexFromString($this->cachedHighestColumn) < Coordinate::columnIndexFromString($aCoordinates[0])) {
              $this->cachedHighestColumn = $aCoordinates[0];
          }
          $this->cachedHighestRow = max($this->cachedHighestRow, $aCoordinates[1]);
  
          // Cell needs appropriate xfIndex from dimensions records
          //    but don't create dimension records if they don't already exist
          $rowDimension = $this->getRowDimension($aCoordinates[1], false);
          $columnDimension = $this->getColumnDimension($aCoordinates[0], false);
  
          if ($rowDimension !== null && $rowDimension->getXfIndex() > 0) {
              // then there is a row dimension with explicit style, assign it to the cell
              $cell->setXfIndex($rowDimension->getXfIndex());
          } elseif ($columnDimension !== null && $columnDimension->getXfIndex() > 0) {
              // then there is a column dimension, assign it to the cell
              $cell->setXfIndex($columnDimension->getXfIndex());
          }
  
          return $cell;
      }
docs: Create a new cell at the specified coordinate.
  
  @param string $pCoordinate Coordinate of the cell
  
  @return Cell Cell that was created