Custom walker with acceskeys (updated)

class nav_walker extends Walker_Nav_Menu
{
      function start_el(&$output, $item, $depth, $args)
      {
           global $wp_query;
           $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';

           $class_names = $value = '';

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

            $current_indicators = array('current-menu-item', 'current-menu-parent', 'current-menu-ancestor', 'current_page_item', 'current_page_parent', 'current_page_ancestor');

            $newClasses = array();

            foreach($classes as $el){
                //check if it's indicating the current page, otherwise we don't need the class
                if (in_array($el, $current_indicators)){
                    array_push($newClasses, $el);
                }
            }

           $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $newClasses), $item ) );
           if($class_names!='') $class_names = ' class="'. esc_attr( $class_names ) . '"';


           $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        ) .'"' : '';

           //accesskeys
           global $wpdb;
           global $access_keys;
           $sql = $wpdb->get_results('SELECT term_taxonomy_id FROM '.$wpdb->term_relationships.' WHERE object_id = '.$item->db_id);
           $menu_id = intval($sql[0]->term_taxonomy_id);

            if(count($access_keys[$menu_id])){
                if($access_keys[$menu_id][$item->ID] != ''){
                    $attributes .= ' accesskey="'.$access_keys[$menu_id][$item->ID].'"';
                }
            }
           //end acceskeys

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

            $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
           }
}