PHPExcel method to modify existing Excel

require_once './Classes/PHPExcel/IOFactory.php';
  $filePath = './Template.xlsx';
  //读取文件
  if (!file_exists($filePath)) {
     exit("you dont have ");
  }
  $objPHPExcel = PHPExcel_IOFactory::load($filePath);
  $sheet = $objPHPExcel->getSheet(0); // 读取第一個工作表
  $highestColumm = $sheet->getHighestColumn(); // 取得总列数
  $highestRow = $sheet->getHighestRow(); // 取得总行数
  /** 循环读取每个单元格的数据 */
  $i = 2;
  foreach ($list as $key => $value) {
      $objPHPExcel->setActiveSheetIndex(0)
            ->setCellValue('Z'.$i, $value['demo'])
            ->setCellValue('AA'.$i, $value['demo']);
      $i++;
  }
  $objPHPExcel->getActiveSheet()->setTitle('Simple');
  $objPHPExcel->setActiveSheetIndex(0);
  /** 输出到指定目录 */
  $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
  $objWriter->save('simple.xlsx');//文件保存路径
  /** 输出到浏览器直接下载打开 */
  $file_name = 'batchTemplate.xlsx';
  header('Content-Type:application/vnd.ms-excel'); //指定下载文件类型
  header('Content-Disposition: attachment; filename="'.$file_name.'"'); //指定下载文件的描述
  header('Content-Length:'.filesize($input_file)); //指定下载文件的大小
  /** 将文件内容读取出来并直接输出，以便下载 */
  readfile($input_file);