Codeigniter - banner page choose file php errors

I am new in CodeIgniter, I'm making an admin panel for all static pages, option is user click on choose file and select a file click to update banner and its uploaded and display on page but when i directly click on Update Banner button so it shows an php error, now i want to know two things first how I will rectify this error secondly is there any alert thing here so i mention the user to first upload file then click update banner button, please suggest i developerbook chatrandom already omegle provide php errors & coding of banner page.

A PHP Error was encountered
Severity: Notice
Message: Undefined variable: banner
Filename: backend/inside_banner.php
Line Number: 2

A PHP Error was encountered
Severity: Notice
Message: Undefined variable: page_id
Filename: backend/inside_banner.php
Line Number: 9

Code

class Banner extends My_Controller {

    function __construct() {
        parent::__construct();
    }

    public function index() {
        if ($this->input->post('submit')) {
            $upload_data = upload_file('banners', array('jpg|png|jpeg|gif'), '2028');
            if ($upload_data['error_flag']) {
                $this->data['errors']['banner'] = $upload_data['errors'];
                $this->data['data'] = $_POST;
                $this->template->write_view('content', 'backend/banner_view', $this->data);
                $this->template->render();
            } else {
                $posted_data = $_POST;
                $posted_data['file_name'] = $upload_data['upload_data']['file_name'];
                $posted_data['lang_id'] = $this->data['lang_id'];
                $b = new Banners();
                $b->addBanner($posted_data);
                redirect('admin/banner');
            }
        }

    $this->data['page_title'] = 'Add Banner';
    $this->template->add_css('layout/css/form.css');

    $this->data['allBanners'] = BannersTable::getAllBanners($this->data['lang_id']);

    $this->template->write_view('content', 'backend/banner_view', $this->data);
    $this->template->render();
}

public function delete($banner_id) {
    $b = new Banners();
    $b->deleteBanner($banner_id);

    redirect('admin/banner');
}

public function inside($page_id) {
    if ($this->input->post('submit')) {
        $upload_data = upload_file('inside_banners', array('jpg|png|jpeg|gif'), '2028');
        if ($upload_data['error_flag']) {
            $this->data['errors']['banner'] = $upload_data['errors'];
            $this->data['data'] = $_POST;
            $this->template->write_view('content', 'backend/inside_banner', $this->data);
            $this->template->render();
        } else {
            $posted_data = $_POST;
            $posted_data['page_id'] = $page_id;
            $posted_data['file_name'] = $upload_data['upload_data']['file_name'];
            $posted_data['lang_id'] = $this->data['lang_id'];
            $ib = new InsideBanners();
            $ib->addInsideBanner($posted_data);
            redirect('admin/banner/inside/' . $page_id);
        }
    }

    if ($page_id) {
        $this->data['page_title'] = 'Add ' . $page_id . ' Banner';
        $this->template->add_css('layout/css/form.css');

        $this->data['page_id'] = $page_id;
        $this->data['banner'] = InsideBannersTable::getOne($page_id);
        // var_dump($this->data['banner']);exit;

        $this->template->write_view('content', 'backend/inside_banner', $this->data);
        $this->template->render();
    } else {
        redirect('admin/dashboard');
    }
}

public function arrange(){
    $b = new Banners();
    $b->updateBannersOrder($_POST);

    redirect('admin/banner');
}

}

?>

Your $b = new Banners(); will produce nothing, that's why $this->data is empty. You should read some tutorials about Codeigniter and MVC. You should create a Library (called Banner), and create a public function which will return an array containing your data.