How to make a page the home page of another domain
Use Domain Access: https://www.drupal.org/project/domain

Core Drupal + Domain Access can do this, you don't need any code or custom modules. Your Drupal can load different content on each configured domain name. 


Point all domains in Apache/Nginx at the same Drupal install
directory.
Install Drupal using your primary domain.
Create your Landing Page nodes using the default Page Content Type.
Install Domain Access.
Add a new Domain at: http://example.com/admin/structure/domain/create
Edit the Domain settings at: http://example.com/admin/structure/domain/view/:id/config and specify the Site frontpage.
Done.


If you want it in code, you can export the entire configuration with the Features module: https://www.drupal.org/project/features