PHP header下载文件中文名乱码

PT站以前用的环境是lnmp集成环境，现在是原生的apache、php、mysql，话说换了环境才知道lnmp本土化做的真不错 以前很正常的功能现在出现了一些bug，种子下载就出现了问题，下载文件名出现中文乱码的情况，不用说又是编码问题。 先晒一下以前的代码：

header("Content-Type: application/x-bittorrent");
if ( str_replace("Gecko", "", $_SERVER['HTTP_USER_AGENT']) != $_SERVER['HTTP_USER_AGENT'])
{	
	header ("Content-Disposition: attachment; filename=\"$torrentnameprefix.".$row["save_as"].".torrent\"; charset=utf-8");
}
else if ( str_replace("Firefox", "", $_SERVER['HTTP_USER_AGENT']) != $_SERVER['HTTP_USER_AGENT'] )
{
	header ("Content-Disposition: attachment; filename=\"$torrentnameprefix.".$row["save_as"].".torrent\"; charset=utf-8");
}
else if ( str_replace("Opera", "", $_SERVER['HTTP_USER_AGENT']) != $_SERVER['HTTP_USER_AGENT'] )
{
	header ("Content-Disposition: attachment; filename=\"$torrentnameprefix.".$row["save_as"].".torrent\"; charset=utf-8");
}
else if ( str_replace("IE", "", $_SERVER['HTTP_USER_AGENT']) != $_SERVER['HTTP_USER_AGENT'] )
{
	header ("Content-Disposition: attachment; filename=".str_replace("+", "%20", rawurlencode("$torrentnameprefix." . $row["save_as"] .".torrent")));
}
else
{
	header ("Content-Disposition: attachment; filename=".str_replace("+", "%20", rawurlencode("$torrentnameprefix." . $row["save_as"] .".torrent")));
}
print(benc($dict));

换成新环境就不行了，只要是中文就乱码，尝试使用header("Content-type:text/html;charset=utf-8");还有iconv("utf-8","gbk",$row["save_as"]);最终无果，然后各种Google，baidu还是不行，很多文章都是千篇一律，试了好多遍，最终找到解决方案，不过在IE9下面还是有些问题。

header("Content-Type: application/x-bittorrent");
header("Content-Disposition: attachment; filename=" . "$torrentnameprefix." . rawurlencode($row["save_as"] .".torrent") . ";filename*=". "$torrentnameprefix." . rawurlencode($row["save_as"] .".torrent"));
print(benc($dict));