title: Convert json encoded String to json object in FosRestBundle
body: <p>I have a json encoded string in one of my DB fields, e.g.</p>
  
  <p>[{"name":"car","price":"10"}]</p>
  
  <p>I'm using the FosRestBundle to return the DB-Values in json format and the String above is returned - as String - nothing special until here;)</p>
  
  <p>How can this String be converted, so that a Json Object is returned instead?</p>