title: Strange issue with Json & PHP
body: <p>There is any reason why a json string fail to be evaluated (<code>transport.responseText.evalJSON();</code>) on the server but works on my local installation ?</p>
  
  <p>I'm doing a simple ajax request like this one:</p>
  
  <pre><code>new Ajax.Request(
          this.saveUrl, {
              method: 'post',
              parameters: Form.serialize(this.form),
              onLoading: function () {
                  totals.update('&lt;div class="loading-ajax"&gt;&amp;nbsp;&lt;/div&gt;');
              },
              onSuccess: function (transport) {
                  if (transport.status == 200) {
                      var data = transport.responseText.evalJSON();
                      totals.update(data.shipping_method);
                  }
              },
              onFailure: checkout.ajaxFailure.bind(checkout)
          }
      );
  </code></pre>
  
  <p>On server side I output an array containing some html:</p>
  
  <pre><code> $data = array(
              'shipping_method' =&gt; $shipping_method,
              'payment_method' =&gt; $payment_method
          );
  
  echo json_encode($data);       
  </code></pre>
  
  <p>I have tried to valorize <code>$total</code> and '$other' as empty string <code>''</code> but I get the same result:
  <code>transport.responseText.evalJSON();</code> return an <code>"unexpected token"</code></p>
  
  <p>As said above the weird thing is that on my local it works ( the output is the same as the server but js doesn't trigger any error )</p>
  
  <p>I'm struggling with this almost all day ... any help is really appreciate thanks</p>
  
  <p><strong>UPDATE:</strong></p>
  
  <pre><code>console.log(transport.responseText) 
  -&gt; {"shipping_method":"","payment_method":""}
  </code></pre>
  
  <p>Inspecting the server response 'network tab' in chrome I can see a small difference, in comparison to my local: there is a small <code>red dot</code> before the response content if ( is say <code>\ufeff</code> if I move the mouse over it, I'm not sure about the meaning ... )</p>
  
  <p><a href="https://i.stack.imgur.com/puZVQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/puZVQ.png" alt="enter image description here"></a></p>