How to unset form values after success

Ref: http://stackoverflow.com/questions/2802046/codeigniter-form-validation-how-to-unset-form-values-after-success

 $this->load->library('form_validation');

    $this->form_validation->set_rules('firstname', 'First Name', 'required');
    $this->form_validation->set_rules('surname', 'Sur Name', 'required');

    if ($this->form_validation->run() === TRUE)
    {
                    // save data

        $this->session->set_flashdata('message', 'New Contact has been added');
        redirect(current_url());
    }

    $this->load->view('contacts/add', $this->data);