excel导出时列超过26时解决办法

/**
     * 导出数据方法
     * @author 杭州仟奇信息技术有限公司
     */
    protected  function getExcel($fileName,$headArr,$data){
        
        //导入PHPExcel类库，因为PHPExcel没有用命名空间，只能inport导入
        import("Org.Util.PHPExcel");
        import("Org.Util.PHPExcel.Writer.Excel5");
        import("Org.Util.PHPExcel.IOFactory.php");
    
        $date = date("Y_m_d",time());
        $fileName .= "_{$date}.xls";
    
        //创建PHPExcel对象，注意，不能少了\
        $objPHPExcel = new \PHPExcel();
        $objProps = $objPHPExcel->getProperties();
        //设置表头
        $key = 0;
        //print_r($headArr);exit;
        foreach($headArr as $v){
            //注意，不能少了。将列数字转换为字母\
            $colum = \PHPExcel_Cell::stringFromColumnIndex($key);
            $objPHPExcel->setActiveSheetIndex(0) ->setCellValue($colum.'1', $v);
            $key += 1;
        }
        $column = 2;
        $objActSheet = $objPHPExcel->getActiveSheet();
    
        foreach($data as $key => $rows){ //行写入
            $span = 0;
            foreach($rows as $keyName=>$value){// 列写入
                $j = \PHPExcel_Cell::stringFromColumnIndex($span);
                $objActSheet->setCellValue($j.$column, $value);
                $span++;
            }
            $column++;
        }
    
        $fileName = iconv("utf-8", "gb2312", $fileName);
        //重命名表
        $objPHPExcel->getActiveSheet()->setTitle($date);
        //设置字体大小
        $objPHPExcel->getDefaultStyle()->getFont()->setSize(14);
        //设置单元格宽度
        $objPHPExcel->getActiveSheet()->getColumnDimension('A')->setWidth(15);
        //设置默认行高
        $objPHPExcel->getActiveSheet()->getDefaultRowDimension()->setRowHeight(23);
        //设置活动单指数到第一个表,所以Excel打开这是第一个表
        $objPHPExcel->setActiveSheetIndex(0);
        header('Content-Type: application/vnd.ms-excel');
        header("Content-Disposition: attachment;filename=\"$fileName\"");
        header('Cache-Control: max-age=0');
    
        $objWriter = \PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
        $objWriter->save('php://output'); //文件通过浏览器下载
        exit;
    }