$news = M("cms_news");
$news->pageSize = 15;
$news->field = 'id,sUrl,title,hits,addtime,istop';

1.一维数组，一个字段
$news->orderby(['id' => 'asc']);

2. 二维数组，两个字段
$news->orderby(['id' => 'desc', 'hits' => 'asc']);

3.方法传入字符串格式，完整解析
1news->orderby('id desc,hits desc');
$news->orderby('order by id desc,hits desc');

3.orderby直接赋值字符串，完美解析
$news->orderby = 'id desc,hits desc';
$news->orderby = 'order by id desc,hits desc';

字符串格式可包含order by字符串，不分大小写


//调用getList查询
$news->getList();