title: Symfony2. How to allow form to ignore extra fields?
body: <p>I need to post some data to my Symfony form and I use <code>submit()</code> method for this.</p>
  
  <p>But when request contains some extra data, I got error: </p>
  
  <blockquote>
    <p>"This form should not contain extra fields"</p>
  </blockquote>
  
  <p><strong>Is it possible to let form miss the extra data using form configuration ?</strong></p>
  
  <p><strong>Maybe another way for doing this exists?</strong></p>
  
  <p><strong>Notice:</strong> I need <code>submit()</code> method, not <code>handleRequest()</code> because I post my data through cross-domain ajax request, so form cannot be submitted this way. Reason: <code>isValid()</code> return <code>false</code>, because <code>isSubmitted()</code> return false.</p>
  
  <p><strong>P.S.</strong> Of course, I can create service that will be handle my request before passing it to the form, but maybe more elegant way exists.</p>