title: Use an integer field to store the selectged days with bitwise op
body: <p>I'm writing a form which contains all days of the week, but theses days are save in an int field $days. I'm using bitwise-op to display the selected days.</p>
  <pre><code>{% if (day.days b-and 1) == 1 %}
      {{ &quot;sunday&quot; |trans }}
  {% endif %}
  {% if (day.days b-and 2) == 2 %}
      {{ &quot;monday&quot; |trans }}
  {% endif %}
  ....
  </code></pre>
  <p>I don't know how to do to display the checkbox array and convert it into an int and the opposite.</p>
  <p>Here is a part of the formtype</p>
  <pre><code>    $informations = $builder-&gt;create('information', FormType::class, [
          'label'=&gt;'Information',
          'inherit_data' =&gt; true,
          'label_attr' =&gt; ['class'=&gt;'catlabel']])
          -&gt;add('categoryQualityView', ChoiceType::class, [
              'required' =&gt; true,
              'label' =&gt; 'viewQuality',
              'choices' =&gt; PlaceRepository::$categoriesRates,
              'attr' =&gt; [
                  'class' =&gt; 'selectpicker',
              ],
          ])
          -&gt;add('categoryGastronomy', ChoiceType::class, [
              'label' =&gt; 'Gastronomy',
              'required' =&gt; true,
              'choices' =&gt; PlaceRepository::$categoriesGastronomy,
              'attr' =&gt; [
                  'class' =&gt; 'selectpicker',
              ],
          ])
          -&gt;add('price', MoneyType::class, [
              'required' =&gt; false,
              'label' =&gt; 'Price',
          ])
          -&gt;add('days', IntegerType::class, [
              'required' =&gt; false,
              'label' =&gt; 'Days',
          ])
          -&gt;add('description', TextType::class, [
              'required' =&gt; false,
              'label' =&gt; 'Description',
          ])
          ;
  </code></pre>