The web users cannot get to it directly from a link, however, you could write a php script to accept a filename with path, and output that file to the user.
So, for instance, the same script you are using to get the filename/path could be used to also go ahead and output that file to the user using something like the fpassthru function.
Alternatively if you have multiple files you would like for the user to select from, you could have the DB selection script list the available files and add an anchor tag to another script that would pass the information through to the user. (e.g. the DB select script lists 4 files, each with a link to "download.php?filename=/path_to_file/filename.jpg")
Hope this makes sense. 😉
John Cornett