title: Symfony 4, when I try to submit a form it does not work
body: <p>Thanks in advance to those who want to help me. I'm learning symfony 4 and I'm testing to see how to update a database by taking data from a form. So I made sure that it looked for a table on the base of the id and that it filled the form with the correct values ​​of the form. But when I submit, the form-> isSubmitted condition is never verified. Do you have any suggestions?</p>
  
  <pre><code>    public function updateArticle(Request $request, $id)
    {
      $em = $this-&gt;getDoctrine()-&gt;getManager();
      $article = $em-&gt;getRepository(Article::class)-&gt;find($id);
      if (!$article) {
          throw $this-&gt;createNotFoundException(
              'No article found for id '.$id
          );
      }
      $articletext = $article-&gt;getArticle();
      $title = $article-&gt;getTitle();
      $image = $article-&gt;getFeatureimage();
      $category = $article-&gt;getCategory();
      $author = $article-&gt;getAuthor();
      $article-&gt;setArticle($articletext);
      $article-&gt;setTitle($title);
      $article-&gt;setFeatureimage($image);
      $article-&gt;setCategory($category);
      $article-&gt;setAuthor($author);
      $form = $this-&gt;createFormBuilder($article)
          -&gt;add('article', TextareaType::class)
          -&gt;add('title', TextType::class)
          -&gt;add('featureimage', FileType::class, array('data_class' =&gt; null,'required' =&gt; true))
          -&gt;add('category', TextType::class)
          -&gt;add('author', TextType::class)
          -&gt;add('save', SubmitType::class, array('label' =&gt; 'Inserisci articolo'))
          -&gt;getForm();
      if ($form-&gt;isSubmitted()) {
          $article = $form-&gt;getData();
          print_r($article);
          return $this-&gt;redirectToRoute('blog');
        }
        else
          return $this-&gt;render('insert.html.twig', array(
            'form' =&gt; $form-&gt;createView(),
          ));
    }
  </code></pre>