Splitting the website into two

I am thinking about splitting the room reservation website into two: the back end that will basically be a web API on top of the database with all the business rules and a website that doesn't have to handle any of the business logic.

Here's a prototype to retrieve systems settings

<?php
require_once 'vendor/autoload.php';
if(isset($_GET[setting_query]))
{
    $setting = new model\Setting;
    $setting = model\Setting::find($_GET[setting_query]);
    $settingvalue = $setting->get_value();
    echo $settingvalue;
}

I know it doesn't have any authentication built in yet but we will get to that in a bit. I'm not even sure if I want to keep this at all. We will learn more...