Wordpress: List all children pages and include the parent page

gistfile1.php

$child_of = 0;
if (empty($post->post_parent)){
    $child_of = $post->ID;
}
else {
    $child_of = $post->post_parent;
}

// Set defaults
$defaults = array(
    'class'       => $tag,
    'depth'       => 0,
    'show_date'   => '',
    'date_format' => get_option( 'date_format' ),
    'exclude'     => '',
    'include'     => '',
    'child_of'    => $child_of,
    'title_li'    => null,
    'authors'     => '',
    'sort_column' => 'menu_order, post_title',
    'sort_order'  => '',
    'link_before' => '',
    'link_after'  => '',
    'exclude_tree'=> '',
    'meta_key'    => '',
    'meta_value'  => '',
    'offset'      => '',
    'exclude_current_page' => 0
);


$pages = get_pages($defaults);
$pageids = array($child_of);

foreach ($pages as $page) {
    $pageids[]= $page->ID;
}

$defaults['include'] = implode(',',$pageids);
wp_list_pages( $defaults );