if in array with Codeigniter

i have conditional when insert data. this is conditional:

if id_status = 4, save fleet with format date('ymd',strtotime(str_replace('-', '/', $date))).$shift.$exca_id;

and if id_status != 4 save fleet with format date('ymd',strtotime(str_replace('-', '/', $date))).$shift.$status;

i try with this code but when i am insert id_status = 4 format always save with format : date('ymd',strtotime(str_replace('-', '/', $date))).$shift.$status;

this is my code in Controller:

function add_fleet()
    {
        $this->data['unit_list']= $this->munit_list->get_all_unit_list();
        $this->data['status']= $this->mstatus->get_status();

        $this->form_validation->set_rules('date', 'Date', 'required');
        $this->form_validation->set_rules('shift', 'Shift', 'required');
        $this->form_validation->set_rules('exca_id', 'EXCA', 'required');
        $this->form_validation->set_rules('id_status', 'Status', 'required');

        if ($this->form_validation->run() == FALSE) 
        {
            $this->data['contents'] = $this->load->view('fleet',$this->data, true);
            $this->load->view('template/wrapper',$this->data);
        }
        else
        {
            $date =  $this->input->post('date');
            $shift =  $this->input->post('shift');
            $exca_id =  $this->input->post('exca_id');
            $status =  $this->input->post('id_status');

            if ((in_array("id_status", $data)) !== 4 ) {
               $fleet = date('ymd',strtotime(str_replace('-', '/', $date))).$shift.$status;
            }
            else
            {
                $fleet = date('ymd',strtotime(str_replace('-', '/', $date))).$shift.$exca_id;
            }

            $data = array(
                    'date' => $date,
                    'shift' => $shift,
                    'exca_id' => $exca_id,
                    'fleet_status' => $fleet,
                    'id_status' => $status,
                );

            $query = $this->database_three->query("
                select count(id_fleet) as jumlah from fleet 
                where fleet_status = '$fleet'");
            $ans = $query->row(); 

            if ($ans->jumlah > 0)
            {
                $this->session->set_flashdata('message', generateSuccessMessage('Fleet ID Sudah Digunakan'));
                redirect(site_url('fleet/add_fleet'));      
            }
            else
            {
                $this->mfleet->add_fleet($data);
                $this->session->set_flashdata('message', generateErrorMessage('Data berhasil ditambah'));
                redirect(site_url('fleet'));

            }

        }

    }

can you help me how to solve this problem?