How can I add a sub menu to an existing navigation menu in WordPress?

Question

I want to add submenu to a navigation menu in wordPress through code (not through admin panel) and I am totally new to Wordpress. Any help would be greatly appreciated! Thanks!

Answer 1

I got the answer, here it is: I want to add submenus ffrom database to the menu named 'Products'

Create a custom plugin and install it through Admin panel. Inside the functions.php write this code. This is upgrade safe way and will not brake if the theme is updated.

add_filter( 'wp_nav_menu_objects', 'ravs_add_menu_parent_class' );
 function ravs_add_menu_parent_class( $items ) {
  $results = 'SOME SQL QUERY';
  foreach ( $items as $item ) {
    $title = $item->title;
    $ID = $item->ID;
    if($title=='Products')
        $parentId = $ID;
  }
  foreach ( $results as $result ) {
  $name = $result->name;
  $id = $result->id;
  $link = array (
        'title'            => $name,
        'menu_item_parent' => $parentId,
        'ID'               => $id,
        'db_id'            => $id,
        'url'              => 'URL'
    );

  $items[] = (object) $link;
  }
  return $items;   
}

Answer 2

Can you describe why you want to do it through code rather than the admin panel?

Your answer might be found in wp_nav_menu. Search around for how to display submenus… such as described here.

Answer 3

I think you get caught in providing the parent slug to the submenu function. Here is the example code and structure from codex for the function add_submenu_page which may help you understand to get your solution.

add_action( 'admin_menu', 'my_custom_menu' );

function my_custom_menu(){

    //add_menu_page( string $page_title, string $menu_title, string $capability, string $menu_slug, callable $function = '', string $icon_url = '', int $position = null )



    //add_submenu_page( string $parent_slug, string $page_title, string $menu_title, string $capability, string $menu_slug, callable $function = '' );

    add_submenu_page( 'custom-options', 'Edit Image', 'Edit Images', 'manage_categories', 'edit-images', function_to_handle_the_request );
}


function function_to_handle_the_request(){
   print '<div class="wrap">';

    $file = "/path-to-your-file"; //get_stylesheet_directory() may be helpful

    if ( file_exists( $file ) )
        require $file;

    print '</div>';
}