title: Dynamic twig variable names
body: <p>Given an array of variables sent to a twig template, such as:</p>
  
  <pre><code>$form   = $this-&gt;createForm( new ServiceItemType()
                             , $entity
                             , array( 'attr'=&gt;
                                       array(
                                            'em'    =&gt; $this-&gt;EM()
                                           ,'group' =&gt; true
                             ) ) );
  </code></pre>
  
  <p>I want to capture the variables for easy access in twig.  However:</p>
  
  <pre><code>{% for key, value in form.vars.attr %}
      {% set key = value %}
  {% endfor %}
  </code></pre>
  
  <p>remaps the key variable in the for loop.</p>
  
  <p>twig objects to:</p>
  
  <pre><code>{% for key, value in form.vars.attr %}
      {% set {{key}} = value %}
  {% endfor %}
  </code></pre>
  
  <p>And stack as I am aware never seems to address set.  Would anyone who knows, please indicate how to accomplish this variable assignment?</p>