不在对象上下文中时使用$ this - MyBB

Question

所以，我正在使用MyBB论坛，我去调节一个线程，并得到这个错误。

Fatal error: Using $this when not in object context in C:\zpanel\hostdata\sdcore\public_html\forums\inc\class_moderation.php on line 642

第642行的代码是

$this->delete_thread($mergetid);

周围的代码（以防万一）

$db->delete_query("threadsubscriptions", "tid = '{$mergetid}'");

        update_first_post($tid);

        $arguments = array("mergetid" => $mergetid, "tid" => $tid, "subject" => $subject);
        $plugins->run_hooks("class_moderation_merge_threads", $arguments);

        $this->delete_thread($mergetid);

和删除线程函数

function delete_thread($tid)
    {
        global $db, $cache, $plugins;

        $tid = intval($tid);
        $plugins->run_hooks("class_moderation_delete_thread_start", $tid);

        $thread = get_thread($tid);

        $userposts = array();

        // Find the pid, uid, visibility, and forum post count status
        $query = $db->query("
            SELECT p.pid, p.uid, p.visible, f.usepostcounts
            FROM ".TABLE_PREFIX."posts p
            LEFT JOIN ".TABLE_PREFIX."forums f ON (f.fid=p.fid)
            WHERE p.tid='{$tid}'
        ");
        $pids = array();
        $num_unapproved_posts = $num_approved_posts = 0;
        while($post = $db->fetch_array($query))
        {
            $pids[] = $post['pid'];
            $usepostcounts = $post['usepostcounts'];

            if(!function_exists("remove_attachments"))
            {
                require MYBB_ROOT."inc/functions_upload.php";
            }

            // Remove attachments
            remove_attachments($post['pid']);

            // If the post is unapproved, count it!
            if($post['visible'] == 0 || $thread['visible'] == 0)
            {
                $num_unapproved_posts++;
            }
            else
            {
                $num_approved_posts++;

                // Count the post counts for each user to be subtracted
                ++$userposts[$post['uid']];
            }
        }

        // Remove post count from users
        if($usepostcounts != 0)
        {
            if(is_array($userposts))
            {
                foreach($userposts as $uid => $subtract)
                {
                    $db->update_query("users", array('postnum' => "postnum-{$subtract}"), "uid='".intval($uid)."'", 1, true);
                }
            }
        }
        // Delete posts and their attachments
        if($pids)
        {
            $pids = implode(',', $pids);
            $db->delete_query("posts", "pid IN ($pids)");
            $db->delete_query("attachments", "pid IN ($pids)");
            $db->delete_query("reportedposts", "pid IN ($pids)");
        }

        // Implied counters for unapproved thread
        if($thread['visible'] == 0)
        {
            $num_unapproved_posts += $num_approved_posts;
        }

        // Delete threads, redirects, subscriptions, polls, and poll votes
        $db->delete_query("threads", "tid='$tid'");
        $db->delete_query("threads", "closed='moved|$tid'");
        $db->delete_query("threadsubscriptions", "tid='$tid'");
        $db->delete_query("polls", "tid='$tid'");
        $db->delete_query("pollvotes", "pid='".$thread['poll']."'");
        $db->delete_query("threadsread", "tid='$tid'");
        $db->delete_query("threadratings", "tid='$tid'");

        $updated_counters = array(
            "posts" => "-{$num_approved_posts}",
            "unapprovedposts" => "-{$num_unapproved_posts}"
        );

        if($thread['visible'] == 1)
        {
            $updated_counters['threads'] = -1;
        }
        else
        {
            $updated_counters['unapprovedthreads'] = -1;
        }

        if(substr($thread['closed'], 0, 5) != "moved")
        {
            // Update forum count
            update_forum_counters($thread['fid'], $updated_counters);
        }

        $plugins->run_hooks("class_moderation_delete_thread", $tid);

        return true;
    }

我将如何解决这个问题？