数据表：category
id pid name sort

------IndexAction--------------
$category = M('category')->where('pid=0')->order('sort asc')->select();
if(!empty($category)){
foreach($category as $key=>$value){
$value['url']= getUrl($value);
echo $value['url'] .'<br>';
$pid = $value['id'];//字段赋值
$category[$key]['child'] = M('category')->where("pid =$pid")->select();
$category[$key]['child']['url'] = getUrl($category[$key]['child']);
}
}
$this->assign('category',$category);//映射值
-------head.html--------------
<div>
<ul>
<li></li>
<volist name="category" id="vo">
<li><a href="{$vo.url}">{$vo.name}</a></li>
<li>
<volist name="vo['child']" id="sub">
<a href="{$sub.url}">{$sub.name}</a>    
</volist>
</li>
</volist>
</ul>
</div>

调试的结果是一二级菜单项的url没显示，但echo $value['url'] .'<br>';输出的结果是对的。