Wordpress parent template inherit

parent-template-inherit.php

<?php 

function switch_page_template() {
    global $post;
    // Checks if current post type is a page, rather than a post
  if (is_page())
  { 
    // Checks if page is parent, if yes, return
    if ($post->post_parent == 0)
      return true;
    else if ($post->post_parent != $post->ID)
    {
      $parent_page_template = get_post_meta($post->post_parent,'_wp_page_template',true);
 
      $template = TEMPLATEPATH . "/{$parent_page_template}";
      if (file_exists($template)) {
        load_template($template);
        exit;
      }
    }
  }
}
 
add_action('template_redirect','switch_page_template');

?>