I am building this product for practice and I can not fix a problem. I am selecting members from the database and I can not call them uniquely. It is a model for attendance and it does not get unique once I call "allotted groups." I would appreciate it if someone helps me get unique when trying to take the attendance with members in the database.

Code is shown below:

id;
        $alloted_groups = user()->alloted_groups;
        $alloted_groups = str_replace(",","|",$alloted_groups);
        $attendance_cas_group = $this->session->userdata('attendance_cas_group');

        if($attendance_cas_group){
            $alloted_groups = $attendance_cas_group;

            // first check if attendance is taken for the group
            $today_attendance = $this->db->where(['attendance_date' => date('Y-m-d'),'teacher_id'=>$teacher_id,'cas_item_id'=>$alloted_groups])->from('attendance')->count_all_results();

            if($today_attendance > 0){
                $records = [
                    'data' => [],
                    'message' => 'You have already taken attendance for this group students'
                ];
                return $records;
            }

            $query  = "SELECT s.*,c.selected_cas_items FROM app_students AS s";
            $query .= " LEFT JOIN app_cas_submissions AS c ON s.id = c.student_id";
            $query .= " LEFT JOIN app_attendance AS a ON a.student_ids = s.id";
            //$query .= " WHERE FIND_IN_SET(" .$alloted_groups. ",selected_cas_items)";
            $query .= ' WHERE CONCAT(",", selected_cas_items, ",") REGEXP ",('.$alloted_groups.'),"';
            //$query .= ' WHERE c.selected_cas_items LIKE "%'.$alloted_groups.'%"';

            if($id){
                $query .= " AND a.id =".$id;
            }else{
                //$query .= " AND a.id IS NULL";
            }

            $records    =   $this->db->query($query)->result_array();

            if(count($records) == 0){
                $records = [
                    'data' => [],
                    'message' => 'There is no student in your group'
                ];
            }else{
                $records = [
                    'data' => $records,
                    'message' => ''
                ];
            }
            return $records;
        }else{
            $records = [
                'data' => [],
                'message' => 'Please select the CAS group first'
            ];
        }
        return $records;
    }


    public function get($id)
    {
        $current_date = date('Y-m-d');
        $teacher_id = user()->id;
        $attendance = $this->db->where(['id'=>$id])->get('attendance')->row();
        if($attendance)
        {
            
            return $attendance;
        }else{
            return tableObject("attendance");
        }
    }


    public function save($data)
    {
        $this->db->insert_batch("attendance",$data);
        return $this->db->insert_id();
    }

    public function update($data)
    {
        $this->db->update_batch("attendance",$data,'id');
        return $this->db->affected_rows();
    }

    public function getItems()
    {
        $user_id = user()->id;
        $account_type = user()->account_type;

        $start      =   (int)$this->input->post("start");
        $length     =   (int)$this->input->post("length");
        
        $length     =   ($length)?$length:10;
        
        $columns        =   $this->input->post("columns");
        $order          =   $this->input->post("order");
        $order_by       =   (isset($columns[$order[0]["column"]]))?$columns[$order[0]["column"]]['data']:"id";
        $direction      =   (isset($order[0]["dir"]))?$order[0]["dir"]:"desc";
        $teacher_id = user()->id;
        $this->db->select("a.*,IF(teacher_id = ".$user_id.", '1', '0') AS edit_attendance")->from("attendance as a");

        if($account_type == 'teacher')
        {
            $this->db->where("teacher_id",$teacher_id);
        }else if($account_type == 'student'){
            $this->db->where("FIND_IN_SET(".$user_id.",student_ids)",1);
        }

        if($this->input->post('cas_items')){
            $this->db->where("cas_item_id",(int)$this->input->post('cas_items'));
        }

        if($this->input->post('attendance_date')){
            $this->db->where(["a.attendance_date"=>date('Y-m-d',strtotime($this->input->post('attendance_date')))]);
        }

        $search         =   $this->input->post("search");
        if(isset($search["value"]) && !empty($search["value"]))
        {
            $this->db->where(["a.attendance_date"=>date('Y-m-d',strtotime($search["value"]))]);
        }

        if($account_type == 'teacher'){
            $attendance_cas_group = $this->session->userdata('attendance_cas_group');
            if($attendance_cas_group){
                $this->db->where("cas_item_id",(int)$attendance_cas_group);
            }
        }

        //$this->db->join('cas_submissions as s','s.student_id=a.student_ids');
        
        $this->db->order_by($order_by." ".$direction);
        $this->db->limit($length,$start);
        
        $records    =   $this->db->get()->result_array();

        if(count($records) > 0)
        {
            foreach($records as $key => &$val)
            {
                $student_ids = explode(",",$val['student_ids']);
                $list = [];
                foreach($student_ids as $k => $v){
                    $student = $this->db->where(['id'=>$v])->get('students')->row();
                    if($student)
                    {
                        if($account_type == 'student'){
                            if($student->id == $user_id){
                                $list[] = $student->first_name . ' ' . $student->last_name;
                            }
                        }else{
                            $list[] = $student->first_name . ' ' . $student->last_name;
                        }
                    }
                }
                $val['student_ids'] = implode(",",$list);
            }
        }
        return $records;
    }
    
    public function get_total_records()
    {
        $teacher_id = user()->id;
        $account_type = user()->account_type;
        $this->db->select("COUNT(a.id) as TotalRecord")->from("attendance as a");

        if($account_type == 'teacher')
        {
            $this->db->where("teacher_id",$teacher_id);
        }else if($account_type == 'student'){
            $this->db->where("FIND_IN_SET(".$teacher_id.",student_ids)",1);
        }

        if($this->input->post('cas_items')){
            $this->db->where("cas_item_id",(int)$this->input->post('cas_items'));
        }

        if($this->input->post('attendance_date')){
            $this->db->where(["a.attendance_date"=>date('Y-m-d',strtotime($this->input->post('attendance_date')))]);
        }

        $search         =   $this->input->post("search");
        if(isset($search["value"]) && !empty($search["value"]))
        {
            $this->db->where(["a.attendance_date"=>date('Y-m-d',strtotime($search["value"]))]);
        }

        if($account_type == 'teacher'){
            $attendance_cas_group = $this->session->userdata('attendance_cas_group');
            if($attendance_cas_group){
                $this->db->where("cas_item_id",(int)$attendance_cas_group);
            }
        }
        $total_record   =   $this->db->get()->row();
        if($total_record)
        {
            return $total_record->TotalRecord;
        }else{
            return 0;
        }
    }
    
    public function getCategoryDropDown($id)
    {
        $categories     =   $this->db->where("id !=",$id)->get("departments")->result();
        $catArray   =   ["0"=>"-- Select Category --"];
        if(count($categories) > 0){
            foreach($categories as $key=>$val){
                $catArray[$val->id]     =   $val->title;
            }
            $categories     =   $catArray;
        }
        return $categories;
    }

    public function get_cas_items()
    {
        $categories     =   $this->db->where("parent_id !=",0)->get("cas")->result();
        $catArray   =   ["0"=>"-- Select Item --"];
        if(count($categories) > 0){
            foreach($categories as $key=>$val){
                $catArray[$val->id]     =   $val->title;
            }
            $categories     =   $catArray;
        }
        return $categories;
    }

    public function get_cas_groups()
    {
        $user = user();
        if($user->account_type == 'teacher'){
            $alloted_groups = $user->alloted_groups;
            $alloted_groups = explode(",",$alloted_groups);
        }else{
            $alloted_groups = [];
        }
        

        foreach($alloted_groups as $key => $val)
        {
            $this->db->or_where('id',$val);
        }
        $categories     =   $this->db->get("cas")->result();
        $catArray   =   ["0"=>"-- Select CAS group --"];
        if(count($categories) > 0){
            foreach($categories as $key=>$val){
                $catArray[$val->id]     =   $val->title;
            }
            $categories     =   $catArray;
        }
        return $categories;
    }
    
    
    
    
    
    public function delete($id)
    {
        $this->db->where("id",$id)->delete("cas");
        return $this->db->affected_rows();
    }   
    
    public function checkSlug($where)
    {
        return $this->db->where($where)->count_all_results("cas");
    }
}