first.php
Suppose we have a link in first.php like below
<a href="download.php?filename=xyz.mpg">Download</a>
download.php
Suppose xyz.mpg is in /var/www/upload/
then in download.php
<?php
header("Content-type: application/octet-stream");
header("Content-Disposition: attachment; filename=".$GET['filename']);
readfile("/var/www/upload/".$GET['filename']);
?>
this will let u download the file