fix url

protected/models/Session.php

@@ -427,8 +427,9 @@ class Session extends Model {
 
             // 特殊处理红包
             if ($msg_type == self::MSG_TYPE_REDPACK) {
+                $url = 'https:' . URL_SELF . "/s/{$group['group_name']}";
                 $text = "
-[收到MeeChat红包，<a href='https://{$_SERVER['HTTP_HOST']}/s/{$group['group_name']}'>请打开MeeChat查看</a>]";
+[收到MeeChat红包，<a href='{$url}'>请打开MeeChat查看</a>]";
             } else {
                 $text = Utils::decodeRC4($msg);
             }