php file list with forced download

Hi, I just have a simple question that some of you might be able to help me with. Was coding a directory listing for several dirs on a client's server that would list the files and allow users to download them. The question is, is there a way to force download of all files, regardless of their types? i.e., if the list constains a .jpg, the browser will show it instead of asking the user to download. Also for .html, gifs, etc. Thanks. Pag