codeigniter - how to prevent F5 from resubmitting a form - php

Question

I have the following method in my controller:
(shortened version but all the key pieces are here...)
class Widget extends CI_Controller {
public function __construct()
{
parent::__construct();
$this->load->model('widget_model');
$this->load->helper('form');
$this->load->library('form_validation');
}
public function assign()
{
//logic to display form.
if ($this->input->method() == "get" ) {
$data['save_status'] = '';
$data['title'] = 'Assign Widget';
$data['main_content'] = "assign";
$this->load->view('includes/template',$data);
}
else
{
//logic to handle POST
...
$data['save_status'] = 'Sucessfully saved to db';
$data['title'] = 'Assign Widget';
$data['main_content'] = "assign";
$this->load->view('includes/template',$data);
}
}
Everything works, except I don't know what the proper way to clear the form data is... because when I press F5 thinking I'm refreshing my page, it's actually resubmitting the data to the database.
Sorry, i'm sure this is a noob question.
Thanks.
EDIT 1
for now, I added a redirect at the end of post logic like this;
redirect(base_url()."index.php/thesamecontroller/thesamemethod");
and that takes the user to the same page, but without the form data being available.
Is this the best way to handle it?