[users@httpd] hide web content

[Duleep Dissanayaka]

i'm developing a web system using php on linux server. Now I faced some
problem with download function I developed. I want to give permission to
download files only for register users on my system. I developed that part
but problem is if anyone knows the download link file can be downloaded
without any restrictions. I want to stop that kind of download using the web
link. Can you give me some help to resolve that problem please.