Force directly linked file to download - php

Question

Is there any way to provide a direct link to a file and force the browser to download it using PHP?
E.g http://www.website.com/directory/file.jpg
We're dealing with huge files here and Chrome in particular seems to have a problem rendering the image, so all the user sees is a blank screen when visiting the file directly. Even though they can still right-click in the blank screen and download the file it's confusing.
We used to output the files from PHP but we ran into memory problems so switched to providing a direct link instead. The files go up to about 5GB, they aren't all images. We have zips, PDFs, PSDs etc.
Currently, the file is requested through a PHP script which accepts the ID of the file and get its URL. The PHP script then redirects to the user to full URL of the file.
How can we ensure that downloads are forced and we don't run into memory issues with the larger files?
Thank you

Answer 1

Just use X-Sendfile but you need to configure it first ... using XSendFilePath
if (file_exists($file)) {
header("X-Sendfile: $file");
header("Content-Type: application/octet-stream");
header(sprintf("Content-Disposition: attachment; filename=\"%s\"", basename($file)));
exit();
}
Note* Please ensure $file is properly escaped before you verify and serve the file
XSendFilePath only works on Apache for other servers please see : Caching HTTP responses when they are dynamically created by PHP

Answer 2

You need to set the headers for force download
$file = 'upload_directory_path/'.$image_name;
if (file_exists($file)) {
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($file));
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
ob_clean();
flush();
readfile($file);
exit;
}

Answer 3

<?php
//file path
$file = 'monkey.gif';
if (file_exists($file)) {
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($file));
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
ob_clean();
flush();
readfile($file);
exit;
}