Nav Menu and display post count

Yep, I’ve got the solution to this problem. You can retrieve number of child items right from menu_items retrieved by wp_get_nav_menu_items. This function retrieves a bunch of post objects containing info about ‘menu_item_parent’.

Inside start_el function of Walker_Nav_Menu class, you can try the match agains $item->ID. This way:

$locations = get_nav_menu_locations();
$menu = wp_get_nav_menu_object( $locations['primary'] );
$menu_items = wp_get_nav_menu_items($menu->term_id);
$count = 0;
foreach( $menu_items as $menu_item ){
    if( $menu_item->menu_item_parent == $item->ID ){
        $count++;           
    }       
}

Than you’ve got the count of children items in $count variable. Here’s the full code:

class Count_Post_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;
    $classes[] = 'menu-item-' . $item->ID;

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

    $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );
    $id = strlen( $id ) ? ' id="' . esc_attr( $id ) . '"' : '';

    $output .= $indent . '<li' . $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        ) .'"' : '';

    /* Code to get children count */
    $locations = get_nav_menu_locations();
    $menu = wp_get_nav_menu_object( $locations['primary'] );
    $menu_items = wp_get_nav_menu_items($menu->term_id);
    $count = 0;
    foreach( $menu_items as $menu_item ){
        if( $menu_item->menu_item_parent == $item->ID ){
            $count++;           
        }       
    }
    $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>';
    if( $count > 0 )
        $item_output .= '('.$count.')';
    $item_output .= $args->after;

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

}