title: paypal express integration confusion and files provided by paypal dont work
body: <p>i used the paypal integration wizard to create the files that i need to integrate paypal into a custom shopping cart and in the paypalfunctions.php page i added the api credentials. i loaded the expresscheckout.php, file provided by the wizard, and got this error</p>
  
  <pre><code>SetExpressCheckout API call failed. Detailed Error Message: 
  Security header is not validShort Error Message: Security 
  errorError Code: 10002Error Severity Code: Error
  </code></pre>
  
  <p>what does it mean?</p>
  
  <p>this is the page i loaded only. currently i have not attached these pages to the commerce site and am only testing the files given by paypal to see if it works before doing any integration.</p>
  
  <pre><code>require_once ("paypalfunctions.php");
  // ==================================
  // PayPal Express Checkout Module
  // ==================================
  
  //'------------------------------------
  //' The paymentAmount is the total value of 
  //' the shopping cart, that was set 
  //' earlier in a session variable 
  //' by the shopping cart page
  //'------------------------------------
  $paymentAmount = "10.45";
  
  //'------------------------------------
  //' The currencyCodeType and paymentType 
  //' are set to the selections made on the Integration Assistant 
  //'------------------------------------
  $currencyCodeType = "USD";
  $paymentType = "Sale";
  
  //'------------------------------------
  //' The returnURL is the location where buyers return to when a
  //' payment has been succesfully authorized.
  //'
  //' This is set to the value entered on the Integration Assistant 
  //'------------------------------------
  $returnURL = "http://www.mysite.com/orderConfirm.php";
  
  //'------------------------------------
  //' The cancelURL is the location buyers are sent to when they hit the
  //' cancel button during authorization of payment during the PayPal flow
  //'
  //' This is set to the value entered on the Integration Assistant 
  //'------------------------------------
  $cancelURL = "http://www.mysite.com/cancelOrder.php";
  
  //'------------------------------------
  //' Calls the SetExpressCheckout API call
  //'
  //' The CallShortcutExpressCheckout function is defined in the file PayPalFunctions.php,
  //' it is included at the top of this file.
  //'-------------------------------------------------
  $resArray = CallShortcutExpressCheckout ($paymentAmount, $currencyCodeType, $paymentType, $returnURL, $cancelURL);
  $ack = strtoupper($resArray["ACK"]);
  if($ack=="SUCCESS" || $ack=="SUCCESSWITHWARNING")
  {
      RedirectToPayPal ( $resArray["TOKEN"] );
  } 
  else  
  {
      //Display a user friendly Error on the page using any of the following error information returned by PayPal
      $ErrorCode = urldecode($resArray["L_ERRORCODE0"]);
      $ErrorShortMsg = urldecode($resArray["L_SHORTMESSAGE0"]);
      $ErrorLongMsg = urldecode($resArray["L_LONGMESSAGE0"]);
      $ErrorSeverityCode = urldecode($resArray["L_SEVERITYCODE0"]);
  
      echo "SetExpressCheckout API call failed. ";
      echo "Detailed Error Message: " . $ErrorLongMsg;
      echo "Short Error Message: " . $ErrorShortMsg;
      echo "Error Code: " . $ErrorCode;
      echo "Error Severity Code: " . $ErrorSeverityCode;
  }
  </code></pre>