title: Why create a separate application for RESTful API?
body: <p>In the guide for Yii 2 it is said:</p>
  
  <blockquote>
    <p>While not required, it is recommended that you develop your RESTful
    APIs as a separate application, different from your Web front end and
    back end for easier maintenance.</p>
  </blockquote>
  
  <p>Source: <a href="http://www.yiiframework.com/doc-2.0/guide-rest-quick-start.html#summary">RESTful Web Services - Quick Start</a></p>
  
  <p>What does this mean? Would this be a completely different application or can it be in the same folder as the 'normal' web application? I've just started with my application so I can change things easily, more or less. But I'm wondering: if I would create another application than my business logic would not be accessible.</p>
  
  <p>Why and how I should create another application? And when it's not required?</p>