fopen("file.csv"): failed to open steam: Permission denied

my program is put in server and run it. I already set the folder permission is 777 and the user is root. Also, php.ini allow_uri_fopen is on. But still not working.

the program is related open, modify and save the .csv file and than download. In the error_log show the permission error.

I use Winscp to remote the server and change the file.

what setting need modify? Or coding need change?

thanks you everybody. My English is not very good. I am so sorry.