Thinkphp中如何實作文章的上一篇與下一篇實例分析

$pre=$m->where('id>"'.$_GET["news"].'"')->limit('1')->select();
$this->assign('pre',$pre);

$next=$m->where(&#39;id<"&#39;.$_GET["news"].&#39;"&#39;)->order(&#39;id desc&#39;)->limit(&#39;1&#39;)->select();
$this->assign(&#39;next&#39;,$next);

<p class="pre_next">
<volist name="pre" id="pre">
<p>上一篇：<a href="http://www...com/Index/newslist?news=<{$pre.id}>&&n=News"><{$pre.title}></a></p>
</volist>
<volist name="front" id="front">
<p>下一篇：<a href="http://www...com/Index/newslist?news=<{$next.id}>&&n=News"><{$next.title}></a></p>
</volist>
</p>

$p=!$pre?&#39;没有了&#39;:&#39;.__URL__.&#39;/cm/&#39;.$pre[&#39;nid&#39;].&#39;"<&#39;.$pre[&#39;title&#39;].&#39;&#39;; 
$this->assign(&#39;pre&#39;,$p);