title: CakePHP 3 default json decode request data doesn't work
body: <p>CakePHP documentation says:</p>
  
  <blockquote>
    <p>Typically REST applications not only output content in alternate data formats, but also accept data in different formats. In CakePHP, the RequestHandlerComponent helps facilitate this. By default, it will decode any incoming JSON/XML input data for POST/PUT requests and supply the array version of that data in $this->request->data.
    <a href="http://book.cakephp.org/3.0/en/development/rest.html" rel="nofollow noreferrer">source</a></p>
  </blockquote>
  
  <p>But my <code>$this-&gt;request-&gt;data</code> is empty array.</p>
  
  <p>In <code>AppController.php</code> I load <code>$this-&gt;loadComponent('RequestHandler');</code> </p>
  
  <p>That's my RequestHandler debug info</p>
  
  <p><a href="https://i.stack.imgur.com/hzuDC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hzuDC.png" alt="enter image description here"></a></p>
  
  <p>My request data:</p>
  
  <p><code>Accept: application/json
  Content-Type: application/json</code></p>
  
  <pre><code>{"store_id": 671}
  </code></pre>
  
  <p>And my request data always is empty, why?</p>