Suggestions for "virtual" directories?

[eluser]EdgeTube[/eluser]
Hi all,

I'm working on a file manager as a part of my program, and am wondering what would be the most efficient way to create "virtual" directory structures for users and store files on the server.

I'm not sure what would work best for having sub-directories in sub-directories, etc... and how to link the files in each directory with the database and the file itself.

Any suggestions would be excellent.

Thanks!