public function export($search)
    {
        header("Content-Type: text/csv");
        header("Content-Disposition: attachment; filename={$filename}.csv");
        header('Cache-Control:must-revalidate,post-check=0,pre-check=0');
        header('Expires:0');
        header('Pragma:public');

        $header = 'ID,时间,订单号';
        $header .= "\n";

        $excel_out = iconv('utf-8', 'gbk', $header);//生成字段
        foreach ($data as $val) {
            $id = iconv('utf-8', 'gbk', $val['id']);
            $dtCreated = iconv('utf-8', 'gbk', $val['dt_created']);
            $order_no = iconv('utf-8', 'gbk', $val['order_no']."\t");
            $excel_out .= "{$id},{$dtCreated},{$order_no}";
            $excel_out .= "\n";
        }
        return $excel_out;
    }

上面是一段导出csv 数据的处理逻辑。导出数据主要有两个问题注意

1. iconv(‘utf-8’, ‘gbk’, ‘原始字段内容’) ，防止execl查看中文乱码，需要转码
2. 数字字符串如20210507102211520088265 订单号，一般会自动转成科学计数法展示，需要添加"\t"制表符，防止转译。iconv(‘utf-8’, ‘gbk’, ‘原始字段内容’."\t")