JS读取PHP中文COOKIE的乱码问题（兼容IE、火狐、...）

PHP设置COOKIE

<?php
    $user_name = "我是好人";
    $time=time() + 3600 * 24 * 30;
    $user_name = mb_convert_encoding($user_name,"UTF-8","GBK");
    setcookie('user_name', urlencode($user_name),$time, "/");
?>

JS读取COOKIE

<script language="javascript">
    var user_name=    decodeURI(getCookie("user_name"));
    alert(user_name);
</script>