function is_tree($pid) { // $pid = The ID of the page we're looking for pages underneath
global $post; // load details about this page
if ( is_page($pid) )
return true; // we're at the page or at a sub page
$anc = get_post_ancestors( $post->ID );
foreach ( $anc as $ancestor ) {
if( is_page() && $ancestor == $pid ) {
return true;
}
}
return false; // we aren't at the page, and the page is not an ancestor
}