PHP递归

　　 public static function getNode($node_arr = [], $pid = 0)
    {
        $node_arr = empty($node_arr) ? self::getAll() : $node_arr;
        $node = [];
        $tem = [];
        foreach ($node_arr as $v) {
            if ($v['pid'] == $pid) {
                $tem = self::getNode($node_arr, $v['id']);
                $tem && $v['child'] = $tem;
                $node[] = $v;
            }
        }
        return $node;
    }