WordPress menu with submenu code

WordPress dynamic menu source code:

File: functions.php

<?php
function register_my_menus(){
    register_nav_menus( array(
		
		'primary-menu' => 'Header Menu',
        'footer-menu' => 'Footer Menu'
		
	) );
}
add_action('init', 'register_my_menus');  
?>

File: header.php

<?php
                                        wp_nav_menu( array(
                                            'menu'              => 'primary-menu',
                                            'container'         => false,
                                            'items_wrap'        => '<ul class="nav-menu">%3$s</ul>',
                                            'container_class'   => false,
                                            'container_id'      => false,
                                            'menu_class'        => 'nav-menu'
                                        )
                                       
                                            
                                        );
                                    ?>  

Output:

WordPress dynamic submenu source code:

File: functions.php

<?php
function register_my_sub_menu( $sorted_menu_items, $args ) {
  if ( isset( $args->sub_menu ) ) {
    $root_id = 0;
    foreach ( $sorted_menu_items as $menu_item ) {
      if ( $menu_item->current ) {
        $root_id = ( $menu_item->menu_item_parent ) ? $menu_item->menu_item_parent : $menu_item->ID;
        break;
      }
    }
    if ( ! isset( $args->direct_parent ) ) {
      $prev_root_id = $root_id;
      while ( $prev_root_id != 0 ) {
        foreach ( $sorted_menu_items as $menu_item ) {
          if ( $menu_item->ID == $prev_root_id ) {
            $prev_root_id = $menu_item->menu_item_parent;
            if ( $prev_root_id != 0 ) $root_id = $menu_item->menu_item_parent;
            break;
          } 
        }
      }
    }
$menu_item_parents = array();
    foreach ( $sorted_menu_items as $key => $item ) {
      if ( $item->ID == $root_id ) $menu_item_parents[] = $item->ID;

      if ( in_array( $item->menu_item_parent, $menu_item_parents ) ) {
        $menu_item_parents[] = $item->ID;
      } else if ( ! ( isset( $args->show_parent ) && in_array( $item->ID, $menu_item_parents ) ) ) {
        unset( $sorted_menu_items[$key] );
      }
    }
    
    return $sorted_menu_items;
  } else {
    return $sorted_menu_items;
  }
}
add_filter( 'my_sub_menu', 'register_my_sub_menu', 10, 2 );
?>

File: direct_parent.php

<?php
wp_nav_menu( array(
  'menu'          => 'primary-menu',
  'sub_menu'      => true,
  'direct_parent' => true
) );
?>