Serialized values

/*
DROP TABLE IF EXISTS tbl_siswa;
CREATE TABLE IF NOT EXISTS tbl_siswa(
    id INT AUTO_INCREMENT PRIMARY KEY,
    nis VARCHAR(10),
    nama VARCHAR(50),
    hobi VARCHAR(255)
);

INSERT INTO tbl_siswa(nis,nama,hobi)
VALUES
('2017010001','Andi','1,4,5'),
('2017010002','Budi','1,2,4'),
('2017010003','Carla','2,3'),
('2017010004','Dewi','3,5'),
('2017010005','Edwin','2,3,4,5');

SELECT * FROM tbl_siswa;
+----+------------+-------+---------+
| id | nis        | nama  | hobi    |
+----+------------+-------+---------+
|  1 | 2017010001 | Andi  | 1,4,5   |
|  2 | 2017010002 | Budi  | 1,2,4   |
|  3 | 2017010003 | Carla | 2,3     |
|  4 | 2017010004 | Dewi  | 3,5     |
|  5 | 2017010005 | Edwin | 2,3,4,5 |
+----+------------+-------+---------+

DROP TABLE IF EXISTS tbl_hobi;
CREATE TABLE IF NOT EXISTS tbl_hobi(
    id INT AUTO_INCREMENT PRIMARY KEY,
    hobi VARCHAR(255)
);

INSERT INTO tbl_hobi(hobi)
VALUES
('membaca'),
('olahraga'),
('traveling'),
('menyanyi'),
('melukis');

SELECT * FROM tbl_hobi;
+----+-----------+
| id | hobi      |
+----+-----------+
|  1 | membaca   |
|  2 | olahraga  |
|  3 | traveling |
|  4 | menyanyi  |
|  5 | melukis   |
+----+-----------+

SELECT
    a.id,a.nis,a.nama, GROUP_CONCAT(b.hobi) AS hobi
FROM
    tbl_siswa a
    JOIN tbl_hobi b ON b.id REGEXP CONCAT('^(',REPLACE(a.hobi,',','|'),')$')
GROUP BY a.id;
+----+------------+-------+-------------------------------------+
| id | nis        | nama  | hobi                                |
+----+------------+-------+-------------------------------------+
|  1 | 2017010001 | Andi  | menyanyi,membaca,melukis            |
|  2 | 2017010002 | Budi  | olahraga,menyanyi,membaca           |
|  3 | 2017010003 | Carla | traveling,olahraga                  |
|  4 | 2017010004 | Dewi  | traveling,melukis                   |
|  5 | 2017010005 | Edwin | menyanyi,melukis,olahraga,traveling |
+----+------------+-------+-------------------------------------+


SELECT
    a.id,a.hobi,IF(b.id IS NULL,'',' selected') AS attribute
FROM
    tbl_hobi a
    LEFT JOIN tbl_siswa b ON (a.id REGEXP CONCAT('^(',REPLACE(b.hobi,',','|'),')$') AND b.id=2)

+----+-----------+-----------+
| id | hobi      | attribute |
+----+-----------+-----------+
|  1 | membaca   |  selected |
|  2 | olahraga  |  selected |
|  3 | traveling |           |
|  4 | menyanyi  |  selected |
|  5 | melukis   |           |
+----+-----------+-----------+
*/

//---
$id_siswa=$_GET['id_siswa'];
$sql="
    SELECT
        a.id,a.hobi,IF(b.id IS NULL,'',' selected') AS attribute
    FROM
        tbl_hobi a
        LEFT JOIN tbl_siswa b ON (a.id REGEXP CONCAT('^(',REPLACE(b.hobi,',','|'),')\$') AND b.id={$id_siswa})
";
$result=mysql_query($sql);
echo "<select multiple name='hobi'>";
while($row=mysql_fetch_assoc($result)){
    echo "<option value='{$row['id']}'{$row['attribute']}>{$row['hobi']}</option>";
}
?>
</select>