PHP mkdir(): permission denied uploading a file will change the folder permission to 411 permission

The reason is that there is something wrong with the permission you give ; for example ：

chmod('public/uploads','0777');
chmod('public/uploads',777);
mkdir('public/uploads','0777');

This is wrong , Or there is no problem testing locally , An error is reported when uploading to the server ：

mkdir(): Permission denied

resolvent ：

You need to remove the quotation marks , Or complete the permission parameters

chmod('public/uploads',0777);
mkdir('public/uploads',0777);

777 perhaps '0777' It's actually octal 01411

So it leads to an error ：mkdir(): Permission denied