递归

    $array = array(
        array('id' => 1, 'pid' => 0, 'name' => '河北省'),
        array('id' => 2, 'pid' => 0, 'name' => '北京市'),
        array('id' => 3, 'pid' => 1, 'name' => '邯郸市'),
        array('id' => 4, 'pid' => 2, 'name' => '朝阳区'),
        array('id' => 5, 'pid' => 2, 'name' => '通州区'),
        array('id' => 6, 'pid' => 4, 'name' => '望京'),
        array('id' => 7, 'pid' => 4, 'name' => '酒仙桥'),
        array('id' => 8, 'pid' => 3, 'name' => '永年区'),
        array('id' => 9, 'pid' => 1, 'name' => '武安市'),
    );


    /**
     * 递归实现无限极分类
     * @param $array 分类数据
     * @param $pid 父ID
     * @param $level 分类级别
     * @return $list 分好类的数组 直接遍历即可 $level可以用来遍历缩进
     */

    function getTree($array, $pid =0, $level = 0){

        //声明静态数组,避免递归调用时,多次声明导致数组覆盖
        static $list = [];
        foreach ($array as $key => $value){
            //第一次遍历,找到父节点为根节点的节点 也就是pid=0的节点
            if ($value['pid'] == $pid){
                //父节点为根节点的节点,级别为0，也就是第一级
                $value['level'] = $level;
                //把数组放到list中
                $list[] = $value;
                //把这个节点从数组中移除,减少后续递归消耗
                unset($array[$key]);
                //开始递归,查找父ID为该节点ID的节点,级别则为原级别+1
                getTree($array, $value['id'], $level+1);
            }
        }
        return $list;
    }

    /*
     * 获得递归完的数据,遍历生成分类
     */
    $array = getTree($array);

    foreach($array as $value){
       echo str_repeat('--', $value['level']), $value['name'].'<br />';
    }

引用

    $array = array(
        array('auth_id' => 100, 'auth_name' => '后台首页', 'auth_pid' => 0),
        array('auth_id' => 116, 'auth_name' => '管理员', 'auth_pid' => 0),
        array('auth_id' => 120, 'auth_name' => '管理员列表', 'auth_pid' => 116),
        array('auth_id' => 121, 'auth_name' => '管理员添加', 'auth_pid' => 116),
        array('auth_id' => 122, 'auth_name' => '数据一览', 'auth_pid' => 100),
        array('auth_id' => 123, 'auth_name' => '更新日志', 'auth_pid' => 100),
        array('auth_id' => 124, 'auth_name' => '猜猜看', 'auth_pid' => 123),
    );


    function generateTree($data){
        //构建一个新数组,key为自己的id,为第二步做铺垫
        $items = array();
        foreach($data as $v){
            $items[$v['auth_id']] = $v;
        }

        $tree = array();
        foreach($items as $k => $item){

            //判断是否是顶级分类
            if(isset($items[$item['auth_pid']])){
                $items[$item['auth_pid']]['son'][] = &$items[$k];   //引用赋值
            }else{
                $tree[] = &$items[$k];
            }
        }
        return $tree;
    }

    $data = generateTree($array);