夺命雷公狗---无限级分类NO3

<?php
    header("Content-Type:text/html;charset=utf-8");
    /*
        无限级分类。牵扯2个应用
        0是-找指定栏目的子栏目
        1是-找指定栏目的子孙栏目，即子孙树
        2是-找指定栏目的父栏目/父父栏目....顶级栏目，即家谱树
    */
    $aarr = array(
        array('id'=>1,'name'=>'安徽','pid'=>0),
        array('id'=>2,'name'=>'海淀','pid'=>7),
        array('id'=>3,'name'=>'浣溪县','pid'=>5),
        array('id'=>4,'name'=>'昌平','pid'=>7),
        array('id'=>5,'name'=>'淮北','pid'=>1),
        array('id'=>6,'name'=>'朝阳','pid'=>7),
        array('id'=>7,'name'=>'北京','pid'=>0),
        array('id'=>8,'name'=>'上地','pid'=>2)
    );
     
    function subtree($arr,$id=0,$lev=1){
        $subs = array(); //子孙树
        foreach($arr as $v){
            if($v['pid'] == $id){
                $v['lev'] = $lev;
                $subs[] = $v;
                $subs = array_merge($subs,subtree($arr,$v['id'],$lev+1));//array_merge让数组粘起来
            }
        }
        return $subs;
    }
    $tree = subtree($aarr,0,1);
    foreach($tree as $v){
        echo str_repeat('&nbsp;&nbsp;',$v['lev']).$v['name'].'<br/>';//str_repeat替换
    }