Sub menu with child and parent

Hi everybody,

i have a menu like this:

item a
item b
subitem 1
subitem 2
subitem 3
item c

When i click on subitem 1, i see only the subitem (1, 2 and 3), but i want to see the parent item b and also item a and c.

I’m using this script but it isn’t what i want because it displays only subitems without the item:
<?php
if ( $post->post_parent ) {
$children = wp_list_pages( array(
‘title_li’ => ”,
‘child_of’ => $post->post_parent,
‘echo’ => 0
) );
$parent_title = get_the_title($post->post_parent);
} else {
$children = wp_list_pages( array(
‘title_li’ => ”,
‘child_of’ => $post->ID,
‘echo’ => 0
) );
}
if ( $children ) : ?>

<?php echo $children; ?>

<?php endif; ?>

Thank you