Support resume or use direct link when download attach file?

phpBB 3 included attach files function, but I want to ask the way how to support resume when download attach files with some Internet download manager like as IDM, falshget,... ? Or how to change the download as id

Code:

http://www.domain.com/forum/download/file.php?id=<file-id-number>

to the direct link ?

Code:

http://www.domain.com/forum/files/<file-name>

I changed sucessfully download method from id link to direct link by these steps at localhost:
Open file \download\file.php, find

Code:

$download_mode = (int) $extensions[$attachment['extension']]['download_mode'];

Replace with

Code:

$download_mode = PHYSICAL_LINK;

When click the link to download attach file, i can download with direct link.

Code:

http://localhost/forum/files/<file-name>

But when I upload this file.php to run on the host, i only can download file with this url

Code:

http://www.domain.com/forum/files/2_9959db6b9ad270aab59e7df34b1ba1b6

Although after rename file name and file extension, i can open this file well, but why 2_9959db6b9ad270aab59e7df34b1ba1b6 and how to fix it?

Thank for reading my post.