Triggering Session Flash Message ( using toastr.js )

When I keep refreshing the page it shows the same flash message >

public function create_deposit(){
    $data =$this->data;
    $customer_info = $data['customer'];
    $customer_id = $customer_info['customer_id'];
    $amount = get_data_value($_GET, 'amount');
    $amount = floatval($amount);
    if($amount<=0){
        $this->session->set_flashdata('error_message', "Invalid request (amount should be larger than zero)");
        redirect(base_url('portal/transaction/index'));
        return false;
    }
    $data['amount'] = $amount;
    if($this->check_submit()){
        $payment_data = array(
            's_id'=>get_data_value($_POST, 's_id'),
            'customer_id'=>$customer_id,
            'amount'=>$amount,
            'payment_mode'=>get_data_value($_POST, 'payment_mode'),
        );
        $dtime = DateTime::createFromFormat("d/m/Y", $_POST['document_date']);
        if(!empty($dtime)){
            $time_slot_stamp = $dtime->getTimestamp();
        }else{
            $time_slot_stamp = time();
        }
        $payment_data['add_timestamp'] = date("Y-m-d", $time_slot_stamp);

        $upload_filename = $this->upload_file();
        //print_r($upload_filename); die;
        if(!empty($upload_filename)){
            $payment_data['proof_image'] = $upload_filename;
        }
        $this->db->insert(DEPOSIT_TB, $payment_data);
        $this->session->set_flashdata('status_message', "Thank you. Your deposit was successful");
        redirect(base_url('portal/transaction/index').'?tab=deposits');
        
        
    }
    $data['page_title'] = "Deposit";
    $this->page->showpage($data);
}

Can I add something session so it shows after 1st submit button not every time I refresh any page in the backend?

And here is the controller-php file code -

defined('BASEPATH') OR exit('No direct script access allowed');

class Customer_controller extends MY_Controller{ protected $data; protected $customer_id; protected $customer_name;

public function __construct(){
    parent::__construct();
    $this->load->model('customer_model');
    $this->load->model('access_log_model');
    $session_data = $this->session->get_userdata();
    $customerInfo = array();
    $customer_id = (isset($session_data['customer']['customer_id'])?$session_data['customer']['customer_id']:0);
    if(!empty($customer_id)){
        $customerInfo = $this->customer_model->get(array('customer_id'=>intval($customer_id)));
        if(empty($customerInfo)){
            $this->session->unset_userdata(array('customer_logged_in','customer'));
        }
    }
    $data['customer']=$customerInfo;
    $data['site_setting']=array();

    $data['status_message'] = $this->session->flashdata('status_message');
    $data['error_message'] = $this->session->flashdata('error_message');
    $this->data=$data;
}

public function index(){
    redirect('portal/login/index');
}

protected function check_login($return_url = '') {
    if(empty($return_url))
        $return_url = get_self_url();
    if (!$this->session->userdata('customer_logged_in')) {
        if($this->check_ajax())
            return $this->json_output_error('Please login');
        else
            redirect(base_url('portal/login?return_url='.urlencode($return_url)));
    }
    $customer_info = $this->session->userdata('customer');
    $this->customer_id=$customer_info['customer_id'];
    $this->customer_name = $customer_info['customer_name'];
}
public function login_with_customer($customer_info) {
    $session_data = array(
        'customer_logged_in' => true,
        'customer' => $customer_info
    );
    $this->session->set_userdata($session_data);
}
protected function add_log($log_data){
    $customer_info = $this->session->userdata('customer');
    if(isset($customer_info['customer_id'])){
        $log_data['add_timestamp'] = TIMESTAMP;
        $log_data['ip'] = get_ip();
        $log_data['customer_id'] = $customer_info['customer_id'];
        $log_data['customer_name'] = $customer_info['customer_name'];
        //$this->log_model->insert($log_data);
    }
}

}