PHP无限极分类

public function getCategoryTree($pid=0,$t=-1)
    {
        $t++;
        static $cat_temp;
        $data = M('keywords_categroy')->findAll(array('pid'=>$pid),'id ASC, category');
        if(!empty($data))
        {
            foreach ($data as $key => $val )
            {
                $val['category'] = str_repeat(' ',$t*3).'├'.$val['category'];
                $val['level'] = $t+1;
                $cat_temp[] = $val;
                $this -> getCategoryTree($val['id'],$t);
            }
        }
        return $cat_temp;
    }