PHP: File cannot be downloaded ("404 Not Found" message) - php

Question

I am working on a website of a client for which I didn't write the code. I have troubles making files downloadable.
It is about a subdomain where users can download course files.
The website files are contained in the folder "courses" (on the root level).
The file for displaying the downloadable course files is contained in
"courses/displayfiles.php".
The downloadable files are contained in a folder in "courses/downloadfolder". Inside this folder, each user has his own
files folder which as its name has the user id.
displayfiles.php: The following code successfully displays all files that can be downloaded by the logged-in user:
$path = "downloadfolder/" . $_SESSION['userId'] . "/";
$files = array();
$output = #opendir($path) or die("$path could not be found");
while ($file = readdir($output)) {
if (($file != "..") and ($file != ".")) {
array_push($files, $file);
}
}
closedir($output);
sort($files);
foreach ($files as $file) {
echo '<a class="imtext" href="downloadfolder/' . $_SESSION['userId'] . '/' . $file . '/">' . $file . '</a><br/>';
}
So what does not work about this code: When a user clicks on a file, I get a "404 Not Found" message that the file was not found. How can this be?
Why does displaying the files totally works fine, but at the same time I get a 404 error when clicking a file? The files path ($path) must be correct, or not? What further investigations do I need to take in order to solve this problem?
* UPDATE *
I decided to modify the files loop as followed (changing the href):
foreach ($files as $file) {
echo '<a class="imtext" href="http://'.$_SERVER['HTTP_HOST']. '/downloadfolder/' . $_SESSION['courseId'] . '/' . $file . '/">' . $file . '</a><br/>';
}
Still, when I click on a file, I get a 404 Not Found error. How can this be?

Answer 1

You have to look where the webroot of your page is, where the php file generating the list is located and wherer the files are.
Your generated link is relative to the php file generating the link, which might not be corresponding to the URL in the browser. I'd try to make this link relative to the webroot (note the leading slash!)
echo '<a class="imtext" href="/courses/downloadfolder/' . $_SESSION['userId'] . '/' . $file . '/">' . $file . '</a><br/>';
If that guessed solution doesn't work please provide the current URL of the page where this links are generated and one generated link, so we can help you better.