title: Symfony post data should not be null in request->get()
body: <p>I have extra field on my form. This extra field not use Symfony Form.
  I want to get values of this extra field in my controller.</p>
  <p>Twig code :</p>
  <pre><code>{% for module in tool.modules %}
         &lt;input type=&quot;checkbox&quot; class=&quot;filled-in&quot; id=&quot;user_access_{{ tool.id }}_{{ module.id }}&quot; name=&quot;user[access_{{ tool.id }}][]&quot; value=&quot;{{ module.id }}&quot;&gt;                                                                                  
     &lt;label for=&quot;user_access_{{ tool.id }}_{{ module.id }}&quot;&gt;{{ module.name }}&lt;/label&gt;
  {% endfor %}
  </code></pre>
  <p>Controller code :</p>
  
  <pre><code>    /**
   * @Route(&quot;/{id}/edit&quot;, name=&quot;user_edit&quot;, methods={&quot;GET&quot;, &quot;POST&quot;})
   */
  public function editUser(Request $request, User $user, ModuleRepository $moduleRepository): Response
  {
      //some code
  
      $form = $this-&gt;createForm(UserType::class, $user, array('user'=&gt;$user, 'category'=&gt;$categ, 'tools'=&gt;$tools));
  
      $form-&gt;handleRequest($request);
  
      if ($form-&gt;isSubmitted() &amp;&amp; $form-&gt;isValid()) {
  
  
          dd($request); // parameter access_278 contains data I want
          dd($request-&gt;request-&gt;get('user[access_278][]')); // GET NULL :(
  </code></pre>
  <p><a href="https://i.stack.imgur.com/ezAAa.png" rel="nofollow noreferrer">Results of dd($request)</a></p>
  <p>(The values I want is for access_278)</p>
  <p>As you can see on the results pic, the request contains the data of access_278.</p>
  <p>Why in : <em><strong>dd($request-&gt;request-&gt;get('user[access_278][]'))</strong></em> I get &quot;null&quot; when I should get the values of the checkboxes?</p>
  <p>Maybe I am using a wrong way to retrieve the data?</p>