Widget doesn't be shown- Wordpress 4.4

I developed new module in wordpress 4.4, i created new widget then added widget title from the back-office.

EveryThing was nice, but i can't display widget form in the front office.

I used this code to display :

<?php dynamic_sidebar('ylgsubscriber');?>

my widget class is:

class ylgsubscriber_widget extends WP_Widget
{
    public function __construct()
    {
        parent::__construct('ylgsubscriber', 'YlgSubscriberWidget',
            array('description' => 'Un formulaire d\'inscription à la newsletter.'));
    }
    /*
    * Form to diesplay in front office
     * @var $args
     * @var $instance
    * */
    public function widget($args, $instance)
    {
        echo $args['before_widget'];
        echo $args['before_title'];
        apply_filters('widget_title', $instance['title']);
        echo $args['after_title'];
        include('views/ylgsubscriber_front.php');
        echo $args['after_widget'];
    }

    /*
     * Admin form
     * @var $instance
     * */
    public function form($instance)
    {
        $title = isset($instance['title']) ? $instance['title'] : '';
        include_once('views/ylgsubscriber_admin.php');
    }
}

via Chebli Mohamed