// Subpage Shortcode
function is_child($page_id_or_slug) {
global $post;
if(!is_int($page_id_or_slug)) {
$page = get_page_by_path($page_id_or_slug);
$page_id_or_slug = $page->ID;
}
if(is_page() && $post->post_parent == $page_id_or_slug ) {
return true;
} else {
return false;
}
}