ifelse

<?php

if( is_page_template('page-design-2.php')) {
 include('includes/functions/header-test.php'); ;}   // if its a page template

elseif( is_page_template('main-page.php')) {
include('includes/admin/slider-options.php');  }   // if its another page template

elseif (is_single()) {
include('includes/functions/header-single.php'); ;}   // if it single

elseif( is_page()) {
 include('includes/functions/header-subpages.php'); ;}   // if its pages

elseif( is_category()) {
 include('includes/functions/header-categories.php'); ;}   // if its the category page

elseif( is_home()) {
 include('includes/functions/header-blog.php'); ;}   // if its the posts page

?>