<?php
class Span_Desktop_Menu_Walker extends Walker_Nav_Menu
{
	// add classes to ul sub-menus
	function start_lvl( &$output, $depth = 0, $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,
				'dropdown'
			  );
		 $class_names = implode( ' ', $classes );
	  
		 // build html
		 $output .= "\n" . $indent . '<ul class="' . $class_names . '">' . "\n";
	}
	  
	// add main/sub classes to li's and links
	 function start_el(  &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
		 global $wp_query;
		 $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,            
           ( is_object( $args ) ? ( $args->walker->has_children ?  'drop' : '' ) : null )
		 );
         
		 $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 ) ) );
	  
		 // build html
		 $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 .= ' class="menu-link ' . ( $depth > 0 ? 'sub-menu-link' : 'main-menu-link' ) . '"';
	  
		 $item_output = sprintf( '%1$s<a%2$s>%3$s%4$s%5$s</a>%6$s',
			  ( is_object( $args ) ? $args->before : null ),
			  $attributes,
			  ( is_object( $args ) ? $args->link_before : null ),
			  apply_filters( 'the_title', $item->title, $item->ID ),
			  ( is_object( $args ) ? $args->link_after : null ),
			  ( is_object( $args ) ? $args->after : null )
		 );
	  
		 // build html
		 $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
	}
}