树与二维数组的相互转换

    public function arr2tree($list, $id = 'id', $pid = 'pid', $son = 'children')
    {
        list($tree, $map) = [[], []];
        $map = array_column($list, null, $id);
        foreach ($list as $item) {
            if (isset($item[$pid]) && isset($map[$item[$pid]])) {
                $map[$item[$pid]][$son][] = &$map[$item[$id]];
            } else {
                $tree[] = &$map[$item[$id]];
            }
        }
        unset($map);
        return $tree;
    }
    public function tree2arr($tree = [], $children = 'children')
    {
        if (empty($tree) || !is_array($tree)) {
            return $tree;
        }
        $arrRes = [];
        foreach ($tree as $k => $v) {
            $v['html'] = ' ├'.str_repeat('─',$v['level']).' '.$v['sight_name'].' '.$v['sight_level'];
            $arrTmp = $v;
            unset($arrTmp[$children]);
            $arrRes[] = $arrTmp;
            if (!empty($v[$children])) {
                $arrTmp = $this->tree2arr($v[$children]);
                $arrRes = array_merge($arrRes, $arrTmp);
            }
        }
        return $arrRes;
    }

    public function addGenLevel(&$list, $level = 0) {
        $level = $level + 1;
        foreach ($list as &$value) {
            if (!empty($value['children'])) {
                $this->addGenLevel($value['children'], $level);
            }
            $value['level'] = $level;
        }
    }