PHP code to force download of PDF files

forceDownload("pdfdemo.pdf");
function forceDownload($filename) {
if (false == file_exists($ filename)) {
return false;
}
// http headers
header('Content-Type: application-x/force-download');
header('Content-Disposition: attachment; filename="' . basename($filename) .'"');
header('Content-length: ' . filesize($filename));
// for IE6
 if (false === strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE 6')) {
header('Cache-Control: no-cache, must-revalidate');
}
header('Pragma: no -cache');
// read file content and output
return readfile($filename);;
}

Instructions: The above implements a function forceDownload(), and then by calling this function, PHP can force download files.