PayPal's Express Checkout Sandbox after payment hangs on confirmation - php

Question

I am trying to integrate the PAYPAL Express Checkout which the PHP API. All the code is fine as per the documentation provided by the Paypal. I have added the merchant email and also all the parameter are correct.
But then i use to test, a popup is opened and sandbox account logged in successfully. The item detail is shown over there and after that clicking on the pay now button, the popup is closed and I am left at this page :
https://www.sandbox.paypal.com/webapps/checkout/webflow/sparta/expresscheckoutvalidatedataflow?execution=e1s2
and never returns to the merchant site. And below is the controller code which sends user to paypal :
/**
* Purchase the item and then redirect to the paypal page
* #param type $id
*/
public function purchase($id = '') {
//Loading the required helpers and the libraries which is to be used in this function
$this->load->helper('paypal');
//Get all the item fields from the database
//----------------------------------------------------------------------
$item_fields = itemsfieldsquery::create()->filterByitemid($id)->find();
//Fetch the requested item form the database with its detail
//----------------------------------------------------------------------
$item = itemsquery::create()->filterByid($id)->findOne();
//Fetch the item author detail from the database
//----------------------------------------------------------------------
$user_detail = userprofilequery::create()->filterByid(useritemsquery::create()->filterByitemid($id)->findOne()->getuserid())->findOne();
//set the array wit the kay
foreach ($item_fields as $fields) {
$data[categoriesfieldquery::create()->filterByid($fields->getfieldid())->findOne()->getfieldtype()] = $fields->getfieldvalue();
}
// ==================================
// PayPal Express Checkout Module
// ==================================
//'------------------------------------
//' The paymentAmount is the total value of
//' the purchase.
//'
//' TODO: Enter the total Payment Amount within the quotes.
//' example : $paymentAmount = "15.00";
//'------------------------------------
$paymentAmount = $data['item_price'];
//'------------------------------------
//' The currencyCodeType
//' is 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 = site_url('item/transaction');
//'------------------------------------
//' 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 = site_url('item/transaction');
//'------------------------------------
//' Calls the SetExpressCheckout API call
//'
//' The CallSetExpressCheckout function is defined in the file PayPalFunctions.php,
//' it is included at the top of this file.
//'-------------------------------------------------
$items = array();
$items[] = array('name' => $item->getitemname(), 'amt' => $paymentAmount, 'qty' => 1, 'custom' => $id);
//::ITEMS::
// to add anothe item, uncomment the lines below and comment the line above
// $items[] = array('name' => 'Item Name1', 'amt' => $itemAmount1, 'qty' => 1);
// $items[] = array('name' => 'Item Name2', 'amt' => $itemAmount2, 'qty' => 1);
// $paymentAmount = $itemAmount1 + $itemAmount2;
// assign corresponding item amounts to "$itemAmount1" and "$itemAmount2"
// NOTE : sum of all the item amounts should be equal to payment amount
$resArray = SetExpressCheckoutDG($paymentAmount, $currencyCodeType, $paymentType, $returnURL, $cancelURL, $items);
$ack = strtoupper($resArray["ACK"]);
if ($ack == "SUCCESS" || $ack == "SUCCESSWITHWARNING") {
$token = urldecode($resArray["TOKEN"]);
//Redirect user to the paypal
RedirectToPayPalDG($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"]);
$data['error'] = "SetExpressCheckout API call failed. ";
$data['error'] .= "Detailed Error Message: " . $ErrorLongMsg;
$data['error'] .= "Short Error Message: " . $ErrorShortMsg;
$data['error'] .= "Error Code: " . $ErrorCode;
$data['error'] .= "Error Severity Code: " . $ErrorSeverityCode;
//Paint the page if we got the error
//------------------------------------------------------------------
$this->stencil->paint('item/thanks', $data);
}
return;
}
Can anyone help me out to resolve this error or have any idea?