Get Top Parent Page (Custom WP Function)

functions.php

/** Current Page's Parent */
require_once( 'library/get_top_parent.php' );

get-top-parent.php

<?php
/**
 * Get the Top Parent
 * 04/26/2018
 * @author Jonathan Brockett
 *
 * Requires: WordPress @link https://codex.wordpress.org/
 */


/**
 * Gets the top parent page ID
 * @return string The ID of the top parent page of any child page
 */
function get_the_top_parent() {
  $current_page_id = get_the_ID();
  $current_page_ancestors = get_post_ancestors( $current_page_id->ID );
  $current_page_top_parent = ($current_page_ancestors) ? $current_page_ancestors[count($current_page_ancestors)-1]: $current_page_id;

  return $current_page_top_parent;
}

/**
 * Displays the top parent page ID
 */
function the_top_parent() {
  echo get_the_top_parent();
}