PHPExcelでセルを結合および分割する方法

$objPHPExcel;
$filepath="c:\temp.xlsx";
try {
  $objReader = PHPExcel_IOFactory::createReader('Excel2007');
  $objPHPExcel = $objReader->load($filepath);
} catch (Exception $e) {
  die();
}
$column_index = "A";
//清空要合并的首行单元格值，用于填充合并后的单元格值
$objPHPExcel->getActiveSheet()->setCellValue($column_index.''.$beginRow,'');
//合并单元格,值为''
$objPHPExcel->getActiveSheet()->mergeCells($column_index.''.$beginRow.":".$column_index.''.$endRow);
//拆分单元格,将清空合并前单元格的值并还原合并前单元格的样式
$objPHPExcel->getActiveSheet()->unmergeCells($column_index.''.$beginRow.":".$column_index.''.$endRow);