How to download dxf files(drawing files) using php

[eluser]JasmineFlower[/eluser]
hi,

In my codeigniter having folder(Fence). In one of my php page displays the folder(Fence) files.I gave a link for all these files.I need to download these files with Save As dialog box by click the link.the file format is .dxf format that means AUTOCAD drawing files.

How can i download these files ?