Only one widget?

ok so I changed a bit the code to have a multi instance widget, if you add this to the anythin-popup.php, you should get a standard widget reusable several time :

class apopup extends WP_Widget {

	/**
	 * Register widget with WordPress.
	 */
	public function __construct() {
		parent::__construct(
	 		'apopup', // Base ID
			'Anything Popup Multi', // Name
			array( 'description' => __( 'Widget to add anything popups', 'text_domain' ), ) // Args
		);
	}

	/**
	 * Front-end display of widget.
	 *
	 * @see WP_Widget::widget()
	 *
	 * @param array $args     Widget arguments.
	 * @param array $instance Saved values from database.
	 */
	public function widget( $args, $instance ) {
		extract( $args );
		$title = apply_filters( 'widget_title', $instance['title'] );
		$pop_id = apply_filters( 'widget_title', $instance['popID'] );
		echo $before_widget;
		if ( ! empty( $pop_id ) )
			//echo $before_title . $title . $after_title;
		AnythingPopup($pop_id = $pop_id);
		echo $after_widget;
	}

	/**
	 * Sanitize widget form values as they are saved.
	 *
	 * @see WP_Widget::update()
	 *
	 * @param array $new_instance Values just sent to be saved.
	 * @param array $old_instance Previously saved values from database.
	 *
	 * @return array Updated safe values to be saved.
	 */
	public function update( $new_instance, $old_instance ) {
		$instance = array();
		$instance['title'] = strip_tags( $new_instance['title'] );
		$instance['popID'] = strip_tags( $new_instance['pop_id'] );

		return $instance;
	}

	/**
	 * Back-end widget form.
	 *
	 * @see WP_Widget::form()
	 *
	 * @param array $instance Previously saved values from database.
	 */
	public function form( $instance ) {

		if ( isset( $instance[ 'title' ] ) ) {
			$title = $instance[ 'title' ];
			$pop_id = $instance[ 'popID' ];
		}
		else {
			$title = __( 'New title', 'text_domain' );
			$pop_id = __( 'Popup ID', 'text_domain' );
		}
		?>
		<p>
		<label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
		<input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo esc_attr( $title ); ?>" /><br/><br/>
		<label for="<?php echo $this->get_field_id( 'pop_id' ); ?>"><?php _e( 'ID du popup:' ); ?></label>
		<input class="widefat" id="<?php echo $this->get_field_id( 'pop_id' ); ?>" name="<?php echo $this->get_field_name( 'pop_id' ); ?>" type="text" value="<?php echo esc_attr( $pop_id ); ?>" />
		</p>
		<?php
	}

} // class Foo_Widget
// register Foo_Widget widget
add_action( 'widgets_init', create_function( '', 'register_widget( "apopup" );' ) );