Copy this code and paste it in your HTML
$FILE_NAME = "archivo.zip";
$FILE_PATH = tempnam("/var/tmp", $FILE_NAME);
$fh=fopen($FILE_PATH, "rb");
if (strstr($_SERVER['HTTP_USER_AGENT'], "MSIE"))
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Content-Type: application/octet-stream");
header("Content-type: application/pdf");
header("Content-Type: application/x-msexcel; name=\"$FILE_NAME\"");
//force download dialog with filename:
header("Content-Disposition: attachment; filename=\"$FILE_NAME\"");
//images?
header("Content-Disposition: inline; filename=\"$FILE_NAME\"");
header("Content-Transfer-Encoding: binary\n");
// ???
//return((connection_status()==0) and !connection_aborted());