// ナビゲーションメニューを登録する
function my_theme_register_nav_menu() {
    register_nav_menus( array(
        'primary' => 'メインメニュー', // '場所のID' => '管理画面に表示される名前'
    ) );
}
add_action( 'after_setup_theme', 'my_theme_register_nav_menu' );<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /home/ufaktfca/public_html/wp-content/themes/my-original-theme/functions.php:47) in <b>/home/ufaktfca/public_html/wp-includes/sitemaps/class-wp-sitemaps-renderer.php</b> on line <b>126</b><br />
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://himitsuno-heya123.com/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://himitsuno-heya123.com/wp-sitemap-posts-post-1.xml</loc></sitemap><sitemap><loc>https://himitsuno-heya123.com/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://himitsuno-heya123.com/wp-sitemap-taxonomies-category-1.xml</loc></sitemap><sitemap><loc>https://himitsuno-heya123.com/wp-sitemap-taxonomies-post_tag-1.xml</loc></sitemap><sitemap><loc>https://himitsuno-heya123.com/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>