Totally weird behavior trying to download a Mac DMG file

So I've added a product to my online store that's in .DMG format. Most of the other files are ZIP or PDF. When someone completes a purchase, it downloads the file to them, and this works great: header('Content-Type: application/octet-stream'); header('Content-Disposition: attachment; filename="'.$file_row["filename"].'"'); $size = filesize('../../store/files/'.$file_row['filename']); header('Content-Length: '.$size); readfile('../../store/files/'.$file_row['filename']); So I have my DMG file. I've verified that it automounts and behaves friendly. If you do a direct download, it mounts on the desktop perfectly, and there's all the stuff inside. However, when I complete a test purchase and download using the above code, the DMG file downloads, but then it mounts; the contents are copied into the Downloads folder; the image unmounts; and then deletes. All the contents are delivered, but not in a desirable way. You can see the status change in the Downloads window: Mounting the image Copying the image Unmounting the image Cleaning up WTF?????