title: Zend $this->_helper->json returns array instead of JSON
body: <p>We are developing an API with the ZEND Framework.  Here is an example response </p>
  
  <pre><code>$this-&gt;getResponse()
  -&gt;setHttpResponseCode(200)
  -&gt;appendBody($this-&gt;_helper-&gt;json($client-&gt;toArray()));
  </code></pre>
  
  <p>I imagined $this->_helper->json would return a JSON string but its returning an array (in the dev environment).</p>
  
  <p>I now have the staging server to play with and the very same code is returning JSON strings.</p>
  
  <p>The dev environment is currently a different PHP version (dev is 5.3.1, staging is 5.3.3) is this the cause?  Do these different versions encode JSON differently?  Any idea why this is happening?</p>