Please, do not create a public file proxy on your server, as suggested by "Eye for Video" and "scragar", this is a MEGA HUGE security hole , an EXTREMELY DANGEROUS feature ! Anyone could use it to download anything from the server, including password files, personal cookies, credit card information, stealing identity and even locally crack all username / passwords to remotely access your server and use it for whatever they want... NEVER CREATE A PUBLIC FILE PROXY !!! Geez...
Thank you, all who contributed to this. You've just made things a lot easier for me. Some of my clients didn't know how to right-click a file and what to choose to save the file to their computer. Even with the instructions right there on the page, it was too difficult. Now when they click on a link, their browser asks whether they want to run or save the file. Excellent!
I did make one modification: I put direct_download.php in a dedicated folder and link to it that way: <a href="\[my catch-all folder]\direct_download.php?file=..."> That way, I don't have to remember to copy the php file to every folder in which I'm storing files for download, and I can still use it on any page on the site.
I need to make my site more accessible, especially to mobile users, and more standards-compliant, so I'll be studying here when I have the time.
So, how is it possible to change a MIME attribute of an MP3 file?... The need is to leave the file with his original extension because the same file is managed by a web-mediaplayer, but i'd like to let a download by clicking a specified button.