递归、无限分类

/**
     * 初始化 $treeList
     * @var array
     */
    static public $treeList = array();

    /**
     * 递归处理
     * @param $data
     * @param null $parent
     * @param int $level 层次
     * @return array
     */
    protected function limitTree($data, $parent = null, $level = 1)
    {
        foreach ($data as $key => &$vo) {
            if ($vo['parent'] == $parent) {
                $vo['level'] = $level;
                self::$treeList[] = $vo;
                unset($data[$key]);
                self::limitTree($data, $vo['id'], $level + 1);
            }
        }
        return self::$treeList;
    }