Menu Example

gistfile1.php

<?php 
class nsr_nav extends Walker_Nav_Menu
{
      
// add classes to ul sub-menus
	function start_lvl( &$output, $depth, $args = array()) {
	    // depth dependent classes
	    $indent = ( $depth > 0  ? str_repeat( "\t", $depth ) : '' ); // code indent
	    $display_depth = ( $depth + 1); // because it counts the first submenu as 0
	    $classes = array(
	        'sub-menu',
	        ( $display_depth % 2  ? 'menu-odd' : 'menu-even' ),
	        ( $display_depth >=2 ? 'sub-sub-menu' : '' ),
	        'menu-depth-' . $display_depth
	        );
	    $class_names = implode( ' ', $classes );
	  
	    // build html

	    $output .= "\n" . $indent . '<ul class="' . $class_names . '">';
	}

	function end_lvl( &$output, $depth, $args = array()) {
		$output .= "\n" . $indent . '<span></span></ul>';
	}

	function start_el( &$output, $item, $depth, $args ) {
	    global $wp_query;
//  ****
	    static $count = 1;
		if ( $depth == 0 ) {
			$count = 1;
			$old = get_option('parent_description');
			if ( $item->post_content != $old ) {
				update_option('parent_description', $item->post_content );
			}
		}
		if ( $depth > 0 && $count < 2 ) {
			$output .= '<li class="description">' . get_option('parent_description') . '</li>';
			$count++;
		}
 // ****

	    $indent = ( $depth > 0 ? str_repeat( "\t", $depth ) : '' ); // code indent
	  
	    // depth dependent classes
	    $depth_classes = array(
	        ( $depth == 0 ? 'main-menu-item' : 'sub-menu-item' ),
	        ( $depth >=2 ? 'sub-sub-menu-item' : '' ),
	        ( $depth % 2 ? 'menu-item-odd' : 'menu-item-even' ),
	        'menu-item-depth-' . $depth
	    );
	    $depth_class_names = esc_attr( implode( ' ', $depth_classes ) );
	  
	    // passed classes
	    $classes = empty( $item->classes ) ? array() : (array) $item->classes;
	    $class_names = esc_attr( implode( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) ) );
	    
	    $output .= $indent . '<li id="nav-menu-item-'. $item->ID . '" class="' . $depth_class_names . ' ' . $class_names .'">';
	  	
	    // link attributes
	    $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        ) .'"' : '';
	    $attributes .= ! empty( $item->description ) ? ' data-description="'.esc_attr( $item->description ) . '"' : '';
	    $attributes .= ' class="menu-link ' . ( $depth > 0 ? 'sub-menu-link' : 'main-menu-link' ) . '"';

	    $description = ( ! empty ( $item->description ) && 0 == $depth )
            ? '<li class="nav_desc">' . esc_attr( $item->description ) . '</li>' : '';

	    $item_output = sprintf( '%1$s<a%2$s>%3$s%4$s%5$s</a>%6$s',
	        $args->before,
	        $attributes,
	        $args->link_before,
	        apply_filters( 'the_title', $item->title, $item->ID ),
	        $args->link_after,
	        $args->after
	    );
		
	  
	    // build html
	    $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
	}


}