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// FUNCTION
class description_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;
 
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
        $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        ) .'"' : '';
        $description  = ! empty( $item->description ) ? '<span>'.esc_attr( $item->description ).'</span>' : '';
 
        if($depth != 0) {
            $description = $append = $prepend = "";
        }
 
        $item_output = $args->before;
        $item_output .= '<a itemprop="url"'. $attributes .'>';
        $item_output .= $args->link_before .apply_filters( 'the_title', $item->title, $item->ID );
        $item_output .= $description.$args->link_after;
        $item_output .= '</a>';
        $item_output .= $args->after;
 
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }
}

// TEMA
 wp_nav_menu( array( 'walker' => new description_walker(),	'link_before' => '<span itemprop="name">', 'link_after' => '</span>', 'items_wrap' => '<nav class="nav-primary" role="navigation" itemscope="itemscope" itemtype="http://schema.org/SiteNavigationElement"><ul id="%1$s" class="%2$s">%3$s</ul></nav>') );