Model
// Cek nama dan bulan
    public function cek_bulan($bulan)
    {
        $this->db->where('bulan', $bulan);
        $query = $this->db->get('perhitungan');

        // $count_row = $query->num_rows();

        if($query->num_rows()>0)
        {
            return FALSE;
            return $query->result();
        } else{
            return TRUE;
            return $query->result();
        }
    }

    public function cek_nama($nama)
    {
        $this->db->where('nama', $nama);
        $query = $this->db->get('perhitungan');

        // $count_row = $query->num_rows();

        if($query->num_rows()>0)
        {
            return FALSE;
            return $query->result();
        } else{
            return TRUE;
            return $query->result();
        }
    }
    // End Cek nama dan bulan

    //Replace
    public function replace($nama, $bulan, $data_nilai)
    {
        $this->db->where('nama', $nama);
        $this->db->where('bulan', $bulan);
        return $this->db->update('penilaian',$data_nilai);
    }

Controller
$this->load->library('session');
        for ($i=0; $i < count($v) ; $i++) {

            $data_hitung = array(
                    "id_nilai" => $id_nilai[$i], //nyomot db
                    "nama" => $nama[$i],  //nyomot db
                    "hasil_hitung" => $v[$i], //hasil akhir perhitungan
                    "bulan" => $bulan[$i]  //nyomot db
                );
                $this->hitung_model->replace($nama[$i], $bulan[$i], $data_hitung);
                $this->session->set_flashdata('pesan', 'Anda Telah Mengubah Perhitungan Bulan '.$bulan[0]);

            if ($this->hitung_model->cek_nama($nama[$i]) && $this->hitung_model->cek_bulan($bulan[$i]))
            {
                $data_hitung = array(
                    "id_nilai" => $id_nilai[$i],
                    "nama" => $nama[$i],
                    "hasil_hitung" => $v[$i],
                    "bulan" => $bulan[$i]
                );
                $this->hitung_model->replace($nama[$i], $bulan[$i], $data_hitung);
                $this->session->set_flashdata('pesan', 'Anda Telah Mengubah Perhitungan Bulan '.$bulan[0]);
            }
            else
            {
                $data_hitung = array(
                    "id_nilai" => $id_nilai[$i],
                    "nama" => $nama[$i],
                    "hasil_hitung" => $v[$i],
                    "bulan" => $bulan[$i]
                );
                $this->hitung_model->insert($data_hitung);
                $this->session->set_flashdata('pesan', 'Perhitungan Telah di Simpan');
            }
        }