private function getCellsByCellRange($startRow, $startColumn, $endRow, $endColumn)
{
$cells = array();
for ($row = $startRow; $row <= $endRow; $row++) {
for ($column = $startColumn; $column <= $endColumn; $column++) {
$cells[] = $this->getCell($row, $column);
}
}
return $cells;
}