php – 在CodeIgniter中重复插入数据

public function add_product()
  {
    $this->lang->load('log_in','english');
        log_in_check($this->lang->line('log_in_authentication_error'),'admin/log_in');
        $this->lang->load('common','english');
        $data['title'] = $this->lang->line('admin_index_title');
        $this->load->view('admin_template/header',$data);
        $this->load->view('admin_template/left_menu');
    $data['error_msg'] = '';
        if ($this->form_validation->run('add_product') === TRUE)
        {
      $this->admin_model->add_product($this->input->post());
            $this->session->set_flashdata('status_msg',$this->lang->line('add_product_success'));
            redirect(uri_string(),'refresh');
      exit ;
          $data['error_msg'] = $this->lang->line('add_product_invalid_data');
        }
        $this->load->view('admin/add_product');
        //$this->load->view('admin_template/notification');
        $this->load->view('admin_template/footer');  
  }

比我的模型部分简单添加在pastebin http://pastebin.com/WiLHV2sr

public function add_product($data = array())
  {
    $this->db->insert('ishop_product',$data);
    return $this->db->insert_id();
  }

我的问题是在重定向后如果我按ctrl F5或F5而不是数据插入.我是codeigniter的新手.请帮帮我.任何帮助将不胜感激.