title: Trying to use Adaptive Simple Payments but get blank screen
body: <p>I'm trying to figure out how to use Adaptive Simple Payments with Paypal API and trying to test their default code:</p>
  
  <pre><code>$payRequest = new PayRequest();
  
  $receiver = array();
  $receiver[0] = new Receiver();
  $receiver[0]-&gt;amount = "1.00";
  $receiver[0]-&gt;email = "platfo_1255170694_biz@gmail.com";
  $receiverList = new ReceiverList($receiver);
  $payRequest-&gt;receiverList = $receiverList;
  
  $requestEnvelope = new RequestEnvelope("en_US");
  $payRequest-&gt;requestEnvelope = $requestEnvelope; 
  $payRequest-&gt;actionType = "PAY";
  $payRequest-&gt;cancelUrl = "https://devtools-paypal.com/guide/ap_simple_payment/php?cancel=true";
  $payRequest-&gt;returnUrl = "https://devtools-paypal.com/guide/ap_simple_payment/php?success=true";
  $payRequest-&gt;currencyCode = "USD";
  $payRequest-&gt;ipnNotificationUrl = "http://replaceIpnUrl.com";
  
  $sdkConfig = array(
      "mode" =&gt; "sandbox",
      "acct1.UserName" =&gt; "reznik.demarket-facilitator_api1.gmail.com",
      "acct1.Password" =&gt; "BV5GBSV7QBPXJUNR",
      "acct1.Signature" =&gt; "AcK.GqlanslGMma1L2TIOPx.t0xQApMepP-Rt7jundLbNOzkwOhrqbJ4",
      "acct1.AppId" =&gt; "APP-80W284485P519543T"
  );
  
  $adaptivePaymentsService = new AdaptivePaymentsService($sdkConfig);
  $payResponse = $adaptivePaymentsService-&gt;Pay($payRequest); 
  </code></pre>
  
  <p>it should give me json answer like that:</p>
  
  <pre><code>{"responseEnvelope":{"timestamp":"2015-02-26T17:14:06.242-08:00","ack":"Success","correlationId":"aae1f46492b42","build":"15089777"},"payKey":"AP-0SN13003KN641223K","paymentExecStatus":"CREATED"}
  </code></pre>
  
  <p>Why can i get a blank screen without any errors or success messages?</p>