Here is the code:

<?php
//return the name of the top parent page base on a page_id
function getTopParentPostName($myid){
	$mypage = get_page($myid);

	if ($mypage->post_parent == 0){
		return $mypage->post_name;
	}
	else{
		return getTopParentPostName($mypage->post_parent);
	}

}?>

How this work

It works exactly in the same way that wp_dropdown_categories() function. I only have added the “onchange” argument to the original function to make possible the use of the onchange() event, and the obligatory form because the original function doesn’t include it.

Values accepted by “onchange”:

• 0 = It won’t use onchange() event
• 1 = It will use onchange() event

Instalation and configuration

1. Download altrugon_dropdown_categories.zip
2. Unzip the file
3. Place the folder altrugon_dropdown_categories in your directory wp-content/plugins
4. Activate the plugin
5. Paste this line in your code: <?php altrugon_dropdown_categories(’onchange_submit=1′); ?>
6. Enjoy

Versions

• v1.2: Add an empty option. This is necessary when you don’t have a submit button.
• v1.1: Fix the validation XHTML issue. I have enclosed the select box inside a div which also has a class.

Well, that’s all. If you have any question or suggestion don’t hasitate to contact me.