Wordpress: Add Post Count with specific Age to Category Links

functions.php

<?php 

/*  other function.php code goes here...     */


function my_custom_walker( $args ) {
    return array_merge( $args, array( 'walker' => new My_Custom_Walker() ) );
}
add_filter( 'wp_nav_menu_args', 'my_custom_walker' );

/*  class definition */
class My_Custom_Walker extends Walker_Nav_Menu {

    /*  wp function taken from http://codex.wordpress.org/Class_Reference/Walker_Nav_Menu */
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        $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_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';
        $output .= $indent . '<li' . $id . $value . $class_names .'>';
        $atts = array();
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );
        $attributes = '';
        foreach ( $atts as $attr => $value ) {
            if ( ! empty( $value ) ) {
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
                $attributes .= ' ' . $attr . '="' . $value . '"';
            }
        }
        $item_output = $args->before;
        $item_output .= '<a '. $attributes .'>';
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
        /*  since this alters menus global, post count is only appended with category links
              this could also be adapted with post types or parent category ids */
        $item_output .= $item->object == 'category' ? my_count_posts($item->object_id, 14) . '</a>' : '</a>';
        $item_output .= $args->after;
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }

}

/*  takes a category id and the amount of days counted posts are old */
function my_count_posts($catid, $days) {
    global $wpdb;
    $posts = $wpdb->get_results(
        "SELECT $wpdb->posts.*
        FROM $wpdb->posts
        INNER JOIN $wpdb->term_relationships ON ($wpdb->posts.ID = $wpdb->term_relationships.object_id)
        INNER JOIN $wpdb->term_taxonomy ON ($wpdb->term_relationships.term_taxonomy_id = $wpdb->term_taxonomy.term_taxonomy_id)
        WHERE 1=1
        AND $wpdb->term_taxonomy.taxonomy = 'category'
        AND $wpdb->term_taxonomy.term_id IN ('" . $catid . "')
        AND $wpdb->posts.post_type = 'post'
        AND ($wpdb->posts.post_status = 'publish')
        AND DATE({$wpdb->posts}.post_date) > DATE( DATE_SUB( NOW(), INTERVAL " . $days . " DAY ) ) 
        GROUP BY $wpdb->posts.ID"
    );
    return count($posts) > 0 ? ' <span class="badge">' . count($posts) . '</span>' : FALSE;
}

?>