wp register nav menu

wordpress code

register nav menu

<?php
function moderna_manus(){
    
   register_nav_menus(array(
   
       'main_menu' => 'Main Menu'
   ));

}
add_action('init', 'moderna_manus');

fallback page

function theme_fallback_menu(){
    
		echo '<ul class="nav navbar-nav">';
		if ('page' != get_option('show_on_front')) {
			echo '<li><a href="'. site_url() . '/">Home</a></li>';
		}
		wp_list_pages('title_li=');
		echo '</ul>';
}