I found
function download($file,$filename){
$size=filesize(urldecode($file));
$attachment=(
strpos($HTTP_USER_AGENT,"Mozilla/4")===false // Not Moz4
|| // or
strpos($HTTP_USER_AGENT,"MSIE")!==false) // is IE
? ' attachment;'
: '';
header("Content-Disposition:$attachment filename=".urldecode($filename)."");
header("Content-Type: application/octet-stream");
header("Content-Length: $size");
header("Content-Transfer-Encoding: binary");
readfile(urldecode($file));
}
on this forum. This is adequate for me.