PHP Header下载文件在IE文件名中文乱码问题

$filename = "中文.txt"; 
$ua = $_SERVER["HTTP_USER_AGENT"]; 
$encoded_filename = urlencode($filename); 
$encoded_filename = str_replace("+", "%20", $encoded_filename); 
header('Content-Type: application/octet-stream'); 
if (preg_match("/MSIE/", $ua)) { 
header('Content-Disposition: attachment; filename="' . $encoded_filename . '"'); 
} else if (preg_match("/Firefox/", $ua)) { 
header('Content-Disposition: attachment; filename*="utf8''' . $filename . '"'); 
} else { 
header('Content-Disposition: attachment; filename="' . $filename . '"'); 
}

<?php 
$file_name = urlencode($_REQUEST['filename']); 
header("Pragma: public"); header("Expires: 0"); 
header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); 
header("Content-Type: application/force-download"); 
header('Content-Type: application/vnd.ms-excel; charset=utf-8'); 
header("Content-Transfer-Encoding: binary"); 
//开源代码phprm.com 
header('Content-Disposition: attachment; filename='.$file_name); 
echo stripslashes($_REQUEST['content']);