Display website menu using DFS algorithm

We have website menu as the same following image:

We have to print it such as:

MENU
    1 Home
    2 Certification Exam
        2.1 Exam preparation: step by step
        2.2 Exam Topics
        2.3 Exam Experience
    3 Sample questions
        3.1 Oracle
            3.1.1 1Z0-803 (OCA 7)
            3.1.2 1Z0-804 (OCP 7)
            3.1.3 1Z0-805 (Upgrade to Java SE 7)
            3.1.4 1Z0-808 (OCA 8)
            3.1.5 1Z0-809 (OCP 8)
            3.1.6 1Z0-810 (Upgrade SE 7 to 8 OCP)
            3.1.7 1Z0-813 (Upgrade to SE 8 OCP)
    4 My Books
        4.1 My Certification Notes
    5 Articles
    6 News
    7 Mix
    8 Feedbacks
    9 About

Information about website menu is kept in DB as the following format:

CREATE TABLE IF NOT EXISTS `menu` (
  `id` int(11) NOT NULL,
  `parent_id` int(11) NOT NULL,
  `name` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

id	parent_id	name
0	-1	MENU
1	0	Home
2	0	Certification Exam
3	0	Sample questions
4	0	My Books
5	0	Articles
6	0	News
7	0	Mix
8	0	Feedbacks
9	0	About
10	2	Exam preparation: step by step
11	2	Exam Topics
12	2	Exam Experience
13	3	Oracle
14	13	1Z0-803 (OCA 7)
15	13	1Z0-804 (OCP 7)
16	13	1Z0-805 (Upgrade to Java SE 7)
17	13	1Z0-808 (OCA 8)
18	13	1Z0-809 (OCP 8)
19	13	1Z0-810 (Upgrade SE 7 to 8 OCP)
20	13	1Z0-813 (Upgrade to SE 8 OCP)
21	4	My Certification Notes

Website menu as the graph format:

DFS algorithm: