How do you initiate/force a download for files that reside externally in PHP or other language?

Question

If you have images or other files that reside externally, how do force the browser to download the link when a user click on it?

The use of "Content-disposition: attachment;" header would do that, but it is not working for files that resides externally without reading and importing the file locally.

Answer 1

This is not possible. You cannot dictate a client how to handle a different resource than the currently requested one.

You could only use a proxy to fetch the external external file and pass it to the client.

Answer 2

I don't think it is possible to force a file download if you are not controlling the HTTP headers. Content-disposition: attachment is the only way I know of to accomplish this.

Though this is probably not going to work, my only guess would be trying to combine Content-disposition with a Location header:

Content-disposition: attachment; filename=myfile.jpg
Location: http://www.somesite.com/myfile.jpg

(it's a long shot, probably invalid and/or just bad practice)

Answer 3

You can try this by writing in .htaccess file code like this:

<Files *.xls>
  ForceType application/octet-stream
  Header set Content-Disposition attachment
</Files>
<Files *.eps>
  ForceType application/octet-stream
  Header set Content-Disposition attachment
</Files>

Answer 4

You will have to load the resource on the server first. You might want to do some caching also:

<?php
  header("Content-disposition: attachment; filename=myfile.jpg");
  echo file_get_contents("http://host.tld/path/to/myfile.jpg");
?>

Answer 5

I use a combination of the aforementioned "Content-Disposition" header, as well as forcing the type:

header("Content-type: attachment/octet-stream");
header('Content-disposition: attachment; filename="'.$filename.'"');