Rename pdf file to be downloaded on fly

Given: All the uploaded pdf files on server are prefixed with timestamps. Later user can download these files again. These (ugly)filenames would never change again on server.

Question: When I give the option to download PDF file, name of the file looks ugly and lengthy. How can I change this name to something sensible, so that when user downloads this file, name doesn't look weird?

Do I need to make a copy, since renaming the original file is not an option? Wouldn't it be extra overhead for each downloadable file? Obviously deleting the copied开发者_如何学Python file would be another extra step?

Is it possible to rename file once file is completely downloaded on client side?

What do you guys suggest?

Something like this:

<?php
// We'll be outputting a PDF  
header('Content-type: application/pdf');

// It will be called downloaded.pdf  
header('Content-Disposition: attachment; filename="downloaded.pdf"');

// The PDF source is in original.pdf  
readfile('original.pdf');
?> 

I needed to do this for a recent project and was a bit confused on how to implement, but figured it out shortly after seeing Klaus's answer. To further elaborate on Klaus' response:

1) Create a file called, say, "process.php". Modify Klaus's code so that it accepts two parameters: the original filename and the new name. My process.php looks like:

<?php
$file = $_GET['file'];
if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/pdf');
    header('Content-Disposition: attachment; filename='.$_GET['newFile']);
    header('Content-Transfer-Encoding: binary');
    header('Content-Length: ' . filesize($file));
    ob_clean();
    flush();
    readfile($file);
    exit;
}
?>

2) Create a link on your user-facing page that points to the processor script:

<a href="process.php?file=OriginalFile.pdf&newFile=MyRenamedFile.pdf">DOWNLOAD ME</a>

You need to set the desired filename in the Content-Disposition header:

$name = 'desiredname.pdf';
header('Content-Disposition: attachment;filename="' . $name . '"');

But unfortunately this won't be picked up by a certain webbrowser developed by a team in Redmond. If you want to get it to work in that browser as well, then you need to append the very same filename as last part of the request path. For example: http://example.com/pdf/desiredname.pdf.

The filename of the content served is defined in the HTTP headers. Look around the PHP page on headers (also the comments) for more info.

I was doing something similar a while ago, serving files through php (in my case, not to rename them, but to check that the person downloading them was logged in and was allowed to see those files). I found that pdf downloads didn't work in IE unless I also added these headers:

header('Pragma: public');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Content-Transfer-Encoding: binary');

I'm not sure why. Experiment and see what happens.