将csv导出到iOS 9 safari ..无法读取文档

I'm using php to export a csv to mobile safari. I'm getting this error when I try to download the csv.

Does anyone have any ideas?

ini_set('memory_limit', '2048M');

header("Cache-Control: must-revalidate");
header("Pragma: must-revalidate");
header("Content-type: application/vnd.ms-excel");
header("Content-disposition: attachment; filename=Activity.csv");
header("Expires: 0");

i changed content-type to this.. solved it

header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");