Sidebar nav

class Navigation_Widget extends WP_Widget {

	public function __construct() {

		parent::__construct(
			'sidenav',
			__( 'Navigation', 'text_domain' ),
			array(
				'description' => __( 'Sidebar CMS navigation', 'text_domain' ),
			)
		);

	}

	public function widget( $args, $instance ) {

		front end

	}

	public function form( $instance ) {

	}

	public function update( $new_instance, $old_instance ) {

	}

}

function custom_Navigation_Widgetregister_widgets() {
	register_widget( 'Navigation_Widget' );
}
add_action( 'widgets_init', 'custom_Navigation_Widgetregister_widgets' );