Child pages list widget

ml-siblings-navi-widget.php

<?php
/*
Plugin Name: Siblings Navi Widget
Description: Widget with links to all childern of top-level parent or self page
Author: Max Lyuchin
Author URI: http://heartwp.com/
*/

class ML_SiblingsNaviWidget extends WP_Widget {

	function __construct() {
		// Instantiate the parent object
		parent::__construct( false, 'Siblings Navi Widget' );
	}

	function widget( $args, $instance ) {
		
		global $id;

		// Fire early if home or not a page
		if ( is_home() || !is_page() || !$id )
			return;

		$ancestors = get_post_ancestors( $id, 'page' );

		if ( $ancestors ) {
			$parent_id = end( $ancestors );
		} else {
			$parent_id = $id;
		}

		$widget_title = get_the_title( $parent_id );
		$widget_items = wp_list_pages( array(
			'echo' => 0,
			'child_of' => $parent_id,
			'title_li' => '',
		) );

		if ( $widget_items ) {
			// Output
			echo $args['before_widget'];
			echo $args['before_title'];
			echo $widget_title;
			echo $args['after_title'];
			echo $widget_items;
			echo $args['after_widget'];
		}
	}
}

function ml_siblings_register_widgets() {
	register_widget( 'ML_SiblingsNaviWidget' );
}

add_action( 'widgets_init', 'ml_siblings_register_widgets' );