Required Recursive function for parent child relation tree?

Question

Scenario:

i have course that has shifts(morning ,evening ect.) [ course is parent of shift ].
and for every shift there are sections (A Green,A blue ,B ect)[ shift is parent of sections ].

graph:

Current record i get by joins :

    $this->db->select("sections.section_id,c.course_id,s.id as shift_id");
    $this->db->from($this->_table);
    $this->db->join('shift s', 's.id = sections.shift_id', 'left');
    $this->db->join('courses c', 's.course_id = c.course_id', 'left');
    $this->db->join('employees e', 'e.employee_id = sections.head_id', 'left');
    $this->db->distinct();
    $this->db->order_by('section_id', 'desc');
    $this->db->where('c.course_id',$course_id);

query result:

Array
(
    [0] => Array
        (
            [course_id] => 3
            [section_id] => 5
            [shift_id] => 7
        )

[1] => Array
    (
        [course_id] => 2
        [section_id] => 4
        [shift_id] => 5
    )

[2] => Array
    (
        [course_id] => 2
        [section_id] => 3
        [shift_id] => 6
    )

[3] => Array
    (
        [course_id] => 1
        [section_id] => 2
        [shift_id] => 4
    )

[4] => Array
    (
        [course_id] => 1
        [section_id] => 1
        [shift_id] => 4
    )

)

Want result like this:

Array
(
    [course_id 3] => Array
        (
            [shift id] => array
                                (
                                 [section_id] => 5
                                )
        )
[course_id 2] => Array
    (
        [shift_morning] =>array
                            (
                             [section_id] => 4
                            )
        [shift_noon] =>array
                            (
                             [section_id] => 3
                            )
    )
 [course_id 1] => Array
    (
        [shift_morning] =>array
                            (
                             [section_id] => 2
                            )
        [shift_noon] =>array
                            (
                             [section_id] => 1
                            )
    )
)

any can help please.

Answer 1

I was unable to extrapolate the required information to properly set your shift key from your posted information however all you have to do is modify the switch statement to properly set this key:

$this->db->select("sections.section_id,c.course_id,s.id as shift_id");
$this->db->from($this->_table);
$this->db->join('shift s', 's.id = sections.shift_id', 'left');
$this->db->join('courses c', 's.course_id = c.course_id', 'left');
$this->db->join('employees e', 'e.employee_id = sections.head_id', 'left');
$this->db->distinct();
$this->db->order_by('section_id', 'desc');
$this->db->where('c.course_id',$course_id);
$query = $this->db->get();

$results = array();
foreach ($query->result_array() as $row) {
    switch ($row['shift_id']) {
        case 5:
            $shift = 'morning';
        break;

        case 6:
            $shift = 'noon';
        break;
    }

    $results['course_id '.$row['course_id']]['shift_'.$shift]['section_id'] = $row['section_id'];
}