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

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 r开发者_运维知识库eading and importing the file locally.

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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");
?>

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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.

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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)

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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.'"');

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I use a method similar to this for downloading mp4 files, could work for text files:

$file=fopen('http://example.com/example.txt','r');
header("Content-Type:text/plain");
header("Content-Disposition: attachment; filename="example.txt");
fpassthru($file);

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You can use the download attribute. Just add download = 'filename.extension' to the download link:

 <a link='mysite.com/sfsf.extension' download='filenameuwant.extension'></a>