Math in table

Hello guys, today I wanted to do some maths in a table but, it ain't pleasure...

Basically, I have students, and they have to pay the courses but they can pay later, so in my db i have an "amount" colums, and I want to put a system who can subtract the amount with the deposit and dynamically.

So I have to display subtraction of "amount" and "deposit" in the payment list
AND I have to make sure that every deposit is summed with the previous.

but the template that i'm working on isn't the clearest, and my problems are, I don't know where i can create the result of the substrate and how to display it.

And i don't know how sum data in a db with CI :/


here some functions in the model

this one store the data

PHP Code:

public function storeStudentDue($edit = null, $data = array())
    {
        $data = $data ? $data : $this->xssCleanInput();
        if ($edit) {
            $this->db->where('student_due_id', $edit);
            $data['updated_at'] = date('Y-m-d G:i:s');
            $this->db->update('student_dues', $data);
            $id = $data['student_due_id'];
        } else {
            $data['created_at'] = date('Y-m-d G:i:s');
            $data['created_by'] = adminSession() ? adminSession() : 1;
            if ($data['type'] == 'program') {
                $this->db->where('program_id', $data['program_id']);
            } elseif ($data['type'] == 'semester') {
                $this->db->where('semester_id', $data['semester_id']);
            } else {
                $this->db->where('course_id', $data['course_id']);
            }
            $this->db->where('student_id', $data['student_id']);
            $result = $this->db->get('student_dues');
            if ($result->num_rows() <= 0) {
                $this->db->insert('student_dues', $data);
            }
            $id = $this->db->insert_id();
            return $id;
        }
    } 


Those 2 functions are here to display dynamically the result of the table.

PHP Code:

public function getForDatatable()
    {
        $request = $this->input->get();
        $columns = array(
            "",
            "student_detail",
            "",
            "student_dues.amount",
            "student_dues.versement",
            "student_dues.type",
            "student_dues.description",
            "student_dues.due_date",
            "student_dues.created_at",
            "student_dues.is_paid",
        );
        $orderColumn = $columns[($request['order'][0]['column'] == 0 ? 5 : $request['order'][0]['column'])];
        $orderDirection = $request['order'][0]['dir'];
        $srh = $request['search']['value'];
        $limit = $request['length'];
        $offset = $request['start'];

        $this->db->from('student_dues');
        $this->db->select('
            student_dues.*,
            programs.title as program_title,
            semesters.title as semester_title,
            courses.title as course_title,
            CONCAT('
                .CE_DB_PREFIX.'students.first_name, 
                " ", 
                '.CE_DB_PREFIX.'students.last_name,
                " (", 
                '.CE_DB_PREFIX.'students.email,
                ") - (", 
                '.CE_DB_PREFIX.'student_batches.title,
                ")"
            ) as student_detail
        ');
        if ($srh) {
            $this->db->group_start()
                ->like('students.first_name', $srh)
                ->or_like('students.last_name', $srh)
                ->or_like('students.email', $srh)
                ->or_like('courses.title', $srh)
                ->group_end();
        }
        if (isset($request['is_paid']) && $request['is_paid'] != '') {
            $this->db->where('student_dues.is_paid', $request['is_paid']);
        }
        if (isset($request['type']) && $request['type'] != '') {
            $this->db->where('student_dues.type', $request['type']);
        }
        if (isset($request['program_id']) && $request['program_id'] != '') {
            $this->db->where('student_dues.program_id', $request['program_id']);
        }
        if (isset($request['semester_id']) && $request['semester_id'] != '') {
            $this->db->where('student_dues.semester_id', $request['semester_id']);
        }
        if (isset($request['course_id']) && $request['course_id'] != '') {
            $this->db->where('student_dues.course_id', $request['course_id']);
        }
        if (isset($request['student_batch_id']) && $request['student_batch_id'] != '') {
            $this->db->where('student_batches.student_batch_id', $request['student_batch_id']);
        }
        $this->db->join('programs', 'programs.program_id = student_dues.program_id', 'left');
        $this->db->join('semesters', 'semesters.semester_id = student_dues.semester_id', 'left');
        $this->db->join('courses', 'courses.course_id = student_dues.course_id', 'left');
        $this->db->join('students', 'students.student_id = student_dues.student_id', 'left');
        $this->db->join('student_batches', 'student_batches.student_batch_id = students.student_batch_id', 'left');
        $this->db->group_by("student_dues.student_due_id");
        $this->db->order_by($orderColumn, $orderDirection);
        $this->db->limit($limit, $offset);
        $query = $this->db->get();

        $result = array(
            'data' => $this->prepareDataForTable($query->result()),
            'recordsTotal' => $this->getTotal(),
            'recordsFiltered' => $this->getTotal($srh, $request),
        );

        return $result;
    } 


PHP Code:

private function prepareDataForTable($student_dues)
    {
        $sorted = array();
        foreach ($student_dues as $c) {
            $actions = '';
            $c = objToArr($c);
            if ($c['is_paid'] == 1) {
                $ip_button_text = lang('yes');
                $ip_button_class = 'success';
                $ip_button_title = lang('click_to_disable');
            } else {
                $ip_button_text = lang('no');
                $ip_button_class = 'warning';
                $ip_button_title = lang('click_to_enable');
            }
            
            if (allowedTo('edit_student_due')) {
            $actions .= '
                <button title="'.lang('edit').'" type="button" class="btn btn-primary btn-xs create-or-edit-student-due" data-id="'.$c['student_due_id'].'"><i class="far fa-edit"></i></button>
            ';
            }

            if (allowedTo('delete_student_due')) { 
            $actions .= '
                <button title="'.lang('delete').'" type="button" class="btn btn-danger btn-xs delete-student-due" data-id="'.$c['student_due_id'].'"><i class="far fa-trash-alt"></i></button>
            ';
            }

            $for = '';
            if ($c['program_title'] != '') { 
                $for .= $c['program_title'];
            } elseif ($c['semester_title'] != '') {
                $for .= $c['semester_title'];
            } else {
                $for .= $c['course_title'];
            }
            $for .= '</span>';
            $c['total']=$c['amount'] ;
            $sorted[] = array(
                "<input type='checkbox' class='minimal single-check' data-id='".$c['student_due_id']."' />",
                esc_output($c['student_detail'], 'html'),
                $for,
                esc_output($c['amount'], 'html').' '.setting('default-currency'),
                esc_output($c['versement'], 'html').' '.setting('default-currency'),
                $this->dueTypeDd($c['type']),
                '<span title="'.$c['description'].'">'.trimString($c['description']).'</span>',
                date('d M, Y', strtotime($c['due_date'])),
                date('d M, Y', strtotime($c['created_at'])),
                '<button type="button" class="btn btn-'.$ip_button_class.' btn-xs" data-status="'.$c['is_paid'].'" data-id="'.$c['student_due_id'].'">'.$ip_button_text.'</button>',
                $actions
            );
        }
        return $sorted;
    } 


And here, the StudentDues's controller, and I don't really understood how they work

PHP Code:

/**
     * View Function to display student_dues list view page
     *
     * @return html/string
     */
    public function listView()
    {
        $data['page'] = lang('student_dues');
        $data['menu'] = 'student_dues';

        $pagedata['programs'] = objToArr($this->AdminProgramModel->getAll());
        $pagedata['semesters'] = objToArr($this->AdminSemesterModel->getAll());
        $pagedata['courses'] = objToArr($this->AdminCourseModel->getAll());
        $pagedata['student_batches'] = objToArr($this->AdminStudentBatchModel->getAll());

        $this->load->view('admin/layout/header', $data);
        $this->load->view('admin/student-dues/list', $pagedata);
    }

    /**
     * Function to get data for student_dues jquery datatable
     *
     * @return json
     */
    public function data()
    {
        echo json_encode($this->AdminStudentDueModel->getForDatatable());
    } 


(I can add code if you want)

Huge thanks