Combine multiple menus using the filter wp_nav_menu_items

Question

Is there a way to combine multiple menus in the functions.php file using wp_nav_menu_items()? I need to hook in a second menu to the main menu. The site has two separate menus in the header. One is a drop down and the other is a hamburger. When on mobile the drop down is no good. I need to add the items from the drop down menu (menu 2) to the main menu (hamburger).

below is my current setup. As you can see I am already adding in social and company info to the menu. Now I need to add a second menu.

function add_social_to_wp_menu ( $items, $args ) {

    if ( 'on' === et_get_option( 'divi_show_facebook_icon', 'on' ) ) :
        $social_icons .= '<span class="et-social-icon et-social-facebook">
            <a href="'.esc_url( et_get_option( 'divi_facebook_url', '#' ) ).'" class="icon">
            </a>
        </span>';
    endif;
    if ( 'on' === et_get_option( 'divi_show_twitter_icon', 'on' ) ) :
        $social_icons .= '<span class="et-social-icon et-social-twitter">
            <a href="'.esc_url( et_get_option( 'divi_twitter_url', '#' ) ).'" class="icon">
            </a>
        </span>';
    endif;
    if ( 'on' === et_get_option( 'divi_show_google_icon', 'on' ) ) :
        $social_icons .= '<span class="et-social-icon et-social-google-plus">
            <a href="'.esc_url( et_get_option( 'divi_google_url', '#' ) ).'" class="icon">
            </a>
        </span>';
    endif;
    if ( 'on' === et_get_option( 'divi_show_instagram_icon', 'on' ) ) :
        $social_icons .= '<span class="et-social-icon et-social-instagram">
            <a href="'.esc_url( et_get_option( 'divi_instagram_url', '#' ) ).'" class="icon">
            </a>
        </span>';
    endif;
    if ( 'on' === et_get_option( 'divi_show_youtube_icon', 'on' ) ) :
        $social_icons .= '<span class="et-social-icon et-social-youtube">
            <a href="'.esc_url( et_get_option( 'divi_youtube_url', '#' ) ).'" class="icon">
            </a>
        </span>';
    endif;
    if ( 'on' === et_get_option( 'divi_show_rss_icon', 'on' ) ) :

        $et_rss_url = '' !== et_get_option( 'divi_rss_url' )
            ? et_get_option( 'divi_rss_url' )
            : get_bloginfo( 'rss2_url' );

        $social_icons .= '<span class="menu-item et-social-icon et-social-rss">
            <a href="'.esc_url( $et_rss_url ).'" class="icon">
            </a>
        </span>';
    endif;

    if( 'main-menu' === $args -> menu ) {
        $items .= '<li class="menu-item company-info">'.do_shortcode('[show-company-info]').'</li>';
        $items .= '<li class="menu-item social-networks">'.$social_icons.'</li>';
    }

    return $items;
}
add_filter('wp_nav_menu_items','add_social_to_wp_menu',10,2);

Answer 1

Thankful to the Lord, I found a solution for anyone else that comes across this issue. I took this function from the Wordpress codex and modified it to soot my needs

function get_menu($menu_name) {

    $menu_items = wp_get_nav_menu_items($menu_name);
    $menu_list = '';
    $count = 0;
    $submenu = false;

    foreach( $menu_items as $menu_item ) {

        $link = $menu_item->url;
        $title = $menu_item->title;

        if ( !$menu_item->menu_item_parent ) {

            $parent_id = $menu_item->ID; 

            if(!empty($menu_items[$count + 1]) && $menu_items[ $count + 1 ]->menu_item_parent == $parent_id ) { //Checking for child

                $menu_list .= '<li class="menu-item menu-item-has-children"><a href="'.$link.'">'.$title.'</a>';

            }else{

                $menu_list .= '<li class="menu-item"><a href="'.$link.'">'.$title.'</a>';

            }

        }

        if ( $parent_id == $menu_item->menu_item_parent ) {

            if ( !$submenu ) {

                $submenu = true;
                $menu_list .= '<ul class="sub-menu">';

            }

            $menu_list .= '<li class="menu-item"><a href="'.$link.'">'.$title.'</a></li>';

            if(empty($menu_items[$count + 1]) || $menu_items[ $count + 1 ]->menu_item_parent != $parent_id && $submenu) {

                $menu_list .= '</ul>';
                $submenu = false;

            }

        }

        if (empty($menu_items[$count + 1]) || $menu_items[ $count + 1 ]->menu_item_parent != $parent_id ) { 

            $menu_list .= '</li>';      
            $submenu = false;

        }

        $count++;

    }

    return $menu_list;

}

I then called the function from my menu filter (see function above) like this.

if( 'main-menu' === $args -> menu ) {
        $items .= $fcs_menu = get_menu('SECOND MENU NAME GOES HERE');
        $items .= '<li class="menu-item company-info">'.do_shortcode('[show-company-info]').'</li>';
        $items .= '<li class="menu-item social-networks">'.$social_icons.'</li>';
    }