function not returning value in “functions.php”

Question

I have created a function within my themes functions.php file in order to persist a list of child pages from the level of a parent page while navigating deeper within the hierarchy.
My issue is that when I call the function within the page.php theme file I dont get anything back.

functions.php:

function get_top_parent_children($the_id,$start = 0,$walk = null){

    $current_post = get_post($the_id);
    $walk[] = $current_post;

    if($current_post->post_parent){
        get_top_parent_children($current_post->post_parent,$start,$walk);
    } else {
        $output = array_reverse($walk);
        return get_children($output[$start]->ID);
    }
}

page.php:

<?php get_header(); ?>
<div id="primary" class="clearfix">

    <div id="content">
        <?php the_post(); ?>
        <?php $children = get_top_parent_children($id,1); ?>
        <?php if ( $children ) { ?>
            <section id="post-topic">
                <h2><?php the_title() ?> Topics</h2>
                <ul class="clearfix">
                    <?php foreach( $children as $child){ ?>
                        <li>
                            <a href="<?php echo get_permalink($child->ID) ?>"> <?php echo child->post_title ?> </a>
                        </li>
                    <?php }; ?>
                </ul>
            </section>
        <?php }; ?>
        <?php get_template_part( 'content', 'page' ); ?>
    </div>
    <aside>
        <?php dynamic_sidebar('Page Sidebar'); ?> 
    </aside>
</div>
<?php get_footer(); ?>

Answer 1

I guess you forgot the second return . You have an if with two code paths, but only return a value in the last one. You need:

if($current_post->post_parent){
    return get_top_parent_children(...);
   # ^^^^
} else {
    return get_children(...);
}

Your function is (recursively) calling itself when that condition matches. But you still need to instruct PHP that it should pass on the value to the outer call.