functions.php

<?php function register_my_menu() {
  register_nav_menu('header-menu',__( 'Header Menu' ));
}
add_action( 'init', 'register_my_menu' );
function register_my_menus() {
  register_nav_menus(
    array(
      'header-menu' => __( 'Header Menu' ),
      'extra-menu' => __( 'Extra Menu' )
    )
  );
}add_action( 'init', 'register_my_menus' );?>