Creates a dropdown menu from a WordPress Nav Menu. Useful for sitting alongside regular menu for use in responsive designs, or where there's no room for a regular menu. Gracefully nests.

menu_loader_exploder.php

<?php
	$menu_name = 'topnav'; // or whatever menu you want
	$locations = get_nav_menu_locations();
	$menu = wp_get_nav_menu_object($locations[$menu_name]);
	$menu_items = wp_get_nav_menu_items($menu->term_id, array( 'order' => 'DESC' ));
?>
		
<select class="the-selectors" onChange="document.location.href=this.options[this.selectedIndex].value;">
	<option value="">Please Select</option>
	<?php
	$i = 0;
	
	foreach($menu_items as &$item){
		if($item->menu_item_parent == 0){
			$item->sub_menu = 0;
		}
		elseif(
			isset($menu_items[$i - 1]) 
			&& $item->menu_item_parent == $menu_items[$i - 1]->ID)
		{
			// The last node was my parent. 
			// I am first born, I shall gain a level now.
			$item->sub_menu = $menu_items[$i - 1]->sub_menu + 1;
			
		} elseif(
			isset($menu_items[$i - 1]) 
			&& $item->menu_item_parent == $menu_items[$i - 1]->menu_item_parent)
		{
			// The last node is my sibling. We share a parent. 
			// I shall reference my sibling's sub_menu
			$item->sub_menu = $menu_items[$i - 1]->sub_menu;
			
		} else {
			// I have a parent, but it's not same as last node.
			//  I shall reference my last known sibling
			for($a=$i-1; $a>=0; $a--){
				if(
					isset($menu_items[$a]) 
					&& $item->menu_item_parent == $menu_items[$a]->menu_item_parent)
				{
					$item->sub_menu = $menu_items[$a]->sub_menu;
					break;
				}
			}
		}
		
		echo '<option value="'.$item->url.'">';
		for($z=0; $z<$item->sub_menu; $z++){
			echo '-&nbsp;'; // or whatever characters you want to denote nesting
		}
		
		echo $item->title;
		
		if($item->url == '#'){
			echo '&raquo;'; // indicates non-link parent
		}
		echo '</option>';
		
		$i++;
	}
	?>
</select>

Good job, I have a similar snippet I've written that I use on a regular basis for just this very purpose. It's very useful, given that more and more sites need a responsive alternative or like you said, where a normal menu may not fit a given layout. Thanks for your contribution.

Thanks. I thought about this over the weekend and realized I had nothing in place to indicate a non-link parent (where href="#"), so made a provision for that. I also realized I was making some goofy unnecessary calls to get page_id and whatnot, not realizing the menu_item had all the info I needed, so tidied that up a bit.