title: Symfony 2 - configuration value: array of associative arrays
body: <p>I want to process the following configuration:</p>
  
  <pre><code>acme_demo:
      transitions:
          - { hc_cba: 180 }
          - { cba_hc: -1 }
  </code></pre>
  
  <p>It is clear that I will need to add an arrayNode, like</p>
  
  <pre><code>$rootNode
      -&gt;children()
          -&gt;arrayNode('transitions')
              -&gt;beforeNormalization()
                  -&gt;ifArray()
                      -&gt;then(function($values) {
                          return array('transition' =&gt; $values);
                      })
                  -&gt;end()
              -&gt;end()
          -&gt;end()
      -&gt;end()
  ;
  </code></pre>
  
  <p>but this gives me an InvalidConfigurationException with the message</p>
  
  <pre><code>Unrecognized options "transitions" under "acme_demo.state_machine"
  </code></pre>
  
  <p>How should I process those "inner" values?</p>