Multilevel horizontal menu

I also need to have wp_nav_menu output the sub-menu outside the parent ul… There must be someone out there who has done something similar? Or is the wp_nav_menu function too new? :/

I actually got this handled, sort of. Not entirely sure how much more this taxes the server to render, but it works for now, and renders two independent UL elements.

Basically, I’m calling wp_nav_menu() twice, the 2nd one using a custom walker, as such:

<?php wp_nav_menu(array('theme_location'=>'header-nav', 'container'=>'', 'fallback_cb'=>'', 'depth'=>'1')); ?>
		<?php wp_nav_menu(array('theme_location'=>'header-nav', 'container'=>'', 'fallback_cb'=>'', 'menu_id'=>'subnav', 'container_id'=>'subnav', 'walker'=> new Extract_Current_Submenu())); ?>

Then for the custom walker, taken from another tread on this forum by petersom3000:

class Extract_Current_Submenu extends Walker_Nav_Menu {

	var $found_parents = array();

	function start_el(&$output, $item, $depth, $args) {
			global $wp_query;

			//this only works for second level sub navigations
			$parent_item_id = 0;

			$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';

			$class_names = $value = '';

			$classes = empty( $item->classes ) ? array() : (array) $item->classes;	

			$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
			$class_names = ' class="' . esc_attr( $class_names ) . '"';
			#current_page_item

			// Checks if the current element is in the current selection
			if (strpos($class_names, 'current-menu-item')
				|| strpos($class_names, 'current-menu-parent')
				|| strpos($class_names, 'current-menu-ancestor')
				|| (is_array($this->found_parents) && in_array( $item->menu_item_parent, $this->found_parents )) ) {

				// Keep track of all selected parents
				$this->found_parents[] = $item->ID;

				//check if the item_parent matches the current item_parent
				if($item->menu_item_parent!=$parent_item_id){

					$output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';

					$attributes  = ! empty( $item->attr_title ) ? ' title="'  . esc_attr( $item->attr_title ) .'"' : '';
					$attributes .= ! empty( $item->target )     ? ' target="' . esc_attr( $item->target     ) .'"' : '';
					$attributes .= ! empty( $item->xfn )        ? ' rel="'    . esc_attr( $item->xfn        ) .'"' : '';
					$attributes .= ! empty( $item->url )        ? ' href="'   . esc_attr( $item->url        ) .'"' : '';

					$item_output = $args->before;
					$item_output .= '<a'. $attributes .'>';
					$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
					$item_output .= '</a>';
					$item_output .= $args->after;
				}
				//}
				$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
			}
		}

	function end_el(&$output, $item, $depth) {
		global $found_parents;
		// Closes only the opened LI
		if ( is_array($found_parents) && in_array( $item->ID, $found_parents ) ) {
			$output .= "</li>\n";
		}
	}

	function end_lvl(&$output, $depth) {
		$indent = str_repeat("\t", $depth);
		// If the sub-menu is empty, strip the opening tag, else closes it
		if (substr($output, -22)=="<ul class=\"sub-menu\">\n") {
			$output = substr($output, 0, strlen($output)-23);
		} else {
			$output .= "$indent</ul>\n";
		}
	}

}

That did the trick!