实现代码如下：

{loop subcat($catid) $c}
    {if $c['child']}
    {php $child = subcat($c['catid']);}  
    <div class="wj_fenlei">
        <div class="fenlei_pic">
        	<em><img src="{php echo $c['p_w_picpath'];}" width="298" height="144" alt="" /></em>
            <div class="xmtit">{php echo $c['catname'];}+</div>
            <div class="xian">
            	<span>{php echo "<a href='".$c['url']."' target='_blank'>".$c['catname']."</a>";}</span>
                <div class="xm_a">
                	{loop $child $catc}
                		{php $subcatid[] = $catc['catid'];}
                    	{php echo "<a href='".$catc['url']."' target='_blank'>".$catc['catname']."</a>";}
                    {/loop}
                </div>
            </div>
        </div>
        <ul>     
{php $subcatid  = implode(',', $subcatid);}
{php $arr=explode(',',$subcatid);}
{pc:get sql="SELECT * from v9_news where status=99 and catid in ($subcatid) order by id DESC LIMIT 0,4--" num="6" return="data"}
	{loop $data $r}
             <li> <a href="{$r[url]}" target="_blank" title="{$r['title']}">● [{$CATEGORYS[$r[catid]][catname]}] {str_cut($r['title'],40)}</a></li>  
	{/loop}
{/pc}
        </ul>
        <div class="zs_more">
        {php echo "<a href='".$c['url']."' target='_blank'>我想了解更多".$c['catname']."知识</a>";}
        </div>    	
    </div>
    {php $subcatid = null;}
 	{/if}
{/loop}