How to redirect a parent page to the first child element?

In WordPress, the pages can already be created in a hierarchy, which can help the clarity but also the URL structure. However, if the parent web page should not be filled with content and link directly to the child element, a little coding is required.

Solution: Ideally, you create an empty php file (e.g. blank.php) in a child theme, so that this file is not overwritten when the theme is updated. Finally, insert the following code.

<?php
/*
 * Template Name: Parent Menu
 * Description: Redirects empty parent page to first child page
 */

$child_page = get_pages( "child_of=" . $post->ID . "&sort_column=menu_order" );
if ( $child_page ) {
    $parent_page = $child_page[0];
    wp_redirect( get_permalink( $parent_page->ID ) );
}

In the last step, the template must be changed in the backend on the desired parent page. In the above case, on „Parent Menu“.