控制器:
// 上一篇
$getUpper = Db::name('news')
->where('id','>',$id)
->order('id asc')
->limit(1)
->find();
// 下一篇
$getLower = Db::name('news')
->where('id','<',$id)
->order('id desc')
->limit(1)
->find();
$this->assign('down',$getLower);
$this->assign('up',$getUpper);视图中: