wordpress使用外链图片时缩略图不显示A TimThumb error has occured

错误内容：

A TimThumb error has occured
The following error(s) occured:
You may not fetch images from that site. To enable this site in timthumb, you can either add it to $ALLOWED_SITES and set ALLOW_EXTERNAL=true. Or you can set ALLOW_ALL_EXTERNAL_SITES=true, depending on your security needs.
Query String : src=http://img.xiami.net/images/album/img44/64444/3168251369621567_2.jpg&h=123&w=200&q=90&zc=1&ct=1
TimThumb version : 2.8.13

解决方案：

用timthumb生成外链图片的缩略图时出现以上提示，按照提示的办法操作即可：
编辑timthumb.php，找到ALLOW_ALL_EXTERNAL_SITES，把值改为ture