尝试以下操作:在load hook中,可以输出xml代码。U
function my_menu_pages() {
    $hook = add_submenu_page(
            null, \'Page Title\', \'Page Title\', \'administrator\', \'sub-menu-slug\', function() {
    }
    );
    add_action(\'load-\' . $hook, function() {
        // add your xml code here, 
        // you will get a blank page to start with
        exit;
    });
}
add_action(\'admin_menu\', \'my_menu_pages\');