title: Form shouldn't contain extra fields Symfony 4
body: <p>I am trying to understand how Symfony works, so I tried to create two forms on the same page: one form for the firstname and the other for the email (I want two different forms so two different submit buttons).</p>
  
  <p>I have the error <code>This form should not contain extra fields.</code>with Symfony 4 after I submit the form. The invalid value is the email.The violation message says "<code>{{ extra_fields }}" =&gt; ""email"</code>"</p>
  
  <p>I read in the Symfony documentation that I have to enable the option <code>allow_extra_fields</code>. </p>
  
  <p>So this is what I tried : </p>
  
  <pre><code>$emailForm = $this-&gt;createFormBuilder(['allow_extra_fields' =&gt; true])
                            -&gt;add('email'  )
                            -&gt;add('Submit',SubmitType::class)
                            -&gt;getForm();
  </code></pre>
  
  <p>but it didn't work. How can I remove the error message ? There are a few previous posts about the error but the version 4 of Symfony seems to work differently.</p>
  
  <p>This is a bit more of code : </p>
  
  <pre><code>       $userForm = $this-&gt;createFormBuilder($defaultData)
                      -&gt;add('firstname', TextType::class)
                      -&gt;add('email', EmailType::class)
                      -&gt;add('description', TextType::class)
                      -&gt;add('Submit', SubmitType::class)
                      -&gt;getForm();
  
        $userForm-&gt;handleRequest($request);
  
         $defaultData = ['pass' =&gt; '', 'conf_pass' =&gt; ''];
         $passForm = $this-&gt;createFormBuilder($defaultData)
                  -&gt;add('pass', PasswordType::class, ['label' =&gt; 'Change password'])
                  -&gt;add('conf_pass', PasswordType::class, ['label' =&gt; 'Confirm password'])
                  -&gt;add('Submit', SubmitType::class)
                  -&gt;getForm();
  
        $passForm-&gt;handleRequest($request);
  </code></pre>
  
  <p>I think the problem comes from the fact that I am handling two times, but I'm not sure at all ...</p>