title: Symfony forms Link radiobuttons over CollectionType
body: <p>I have an entity Questions and an entity Answers. The answers are referring to a question and have a field <em>Correct</em> (which is just a Boolean true/false). Each question has 4 answers and of those 4 answers, 1 is correct. </p>
  
  <p>Now I'm implementing a backend form where questions can be added or edited. I use Symfony forms to do this. My formtype builder looks like this:</p>
  
  <p><strong>QuestionType.php</strong></p>
  
  <pre><code>public function buildForm(FormBuilderInterface $builder, array $options): void
  {
       $builder
          -&gt;add('description', TextareaType::class, [
              'label' =&gt; 'admin.question.form.description',
              'required' =&gt; false,
          ])
          -&gt;add('question', TextType::class, [
              'label' =&gt; 'admin.question.form.question',
          ])
          -&gt;add('answers', CollectionType::class,[
              'label' =&gt; 'admin.question.form.answers.answers',
              'entry_type' =&gt; AnswerType::class,
          ]);
  }
  </code></pre>
  
  <p>So I'm using a collection for the answers, which will be 4 in total. This collection is creating AnswerType forms. </p>
  
  <p><strong>AnswerType.php</strong></p>
  
  <pre><code>public function buildForm(FormBuilderInterface $builder, array $options): void
  {
      $builder
          -&gt;add('answer', TextType::class, [
              'label' =&gt; 'admin.question.form.answers.answer',
          ])
          -&gt;add('correct', RadioType::class,[
              'label' =&gt; 'admin.question.form.answers.correct',
          ]);
  }
  </code></pre>
  
  <p>Which is just 2 form elements, an input field for the answer and a radiobutton to indicate whether the answer is true or false. </p>
  
  <p>I want to render those 4 answer fields each with a radiobutton at the end to indicate the correct answer. Unfortunately those radiobuttons are not linked, and each belongs to it's own collection. Each radiobutton is selectable, so every answer can be selected as correct. Which seems logical because there is no way to tell Symfony to group them.</p>
  
  <p>Each has it's own name, and does not belong to each other. How can these checkboxes be linked, or what is a better way to tackle this problem?</p>