Payment gateway not deleting cache (Very Important) Prestashop

Website- designinfo.in

This payment gateway which I have attached is working fine and converts the currency from Dollar or Euro to Rupee before sending the value to the payment gateway (PayuMoney Payment Gateway)

The PROBLEM is that when the customer changes the quantity of products or purchases a new product from the same browser then the price shown in the payment gateway does not change and shows the price of his previous order

Example-

Order 1 ------Final Cost =$1000 Price sent to payment gateway = INR 64000 ( $1000*64 ) .....( If 64 is the exchange rate for $ to INR ).

Order 2-------Final Cost =$2000 Price sent to payment gateway = INR 64000 unchanged ( $1000*64 ) .....( If 64 is the exchange rate for $ to INR ).

In order 2 the price sent should have been INR 128000 ( $2000*64 ).

Therefore the cache is not getting deleted and hence the old price is being shown.

Please note -

          1.The conversion is correct for the first time.

          2. Closing the browser and rebuying the product is not solving the problem.

          3. Changing the browser is solving the problem.

The code below has the payment.php file where the modification for the conversion code ( From Yahoo Finance ) is added.

Please advise what should I change.

<?php
    include(dirname(__FILE__).'/../../config/config.inc.php');
    include(dirname(__FILE__).'/../../init.php');
    include(dirname(__FILE__).'/payu.php');
    $context = Context::getContext();
    $fc = new Frontcontroller();
    $fc->setmedia();

    include(dirname(__FILE__).'/../../header.php');

    global $smarty,$cart,$cookie;

    //Added function for currency converter: This requires the library curl to be installed on the server.
    function currencyConverter($currency_from,$currency_to,$currency_input){
        $yql_base_url = "http://ift.tt/yEhaBW";
        $yql_query = 'select * from yahoo.finance.xchange where pair in ("'.$currency_from.$currency_to.'")';
        $yql_query_url = $yql_base_url . "?q=" . urlencode($yql_query);
        $yql_query_url .= "&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys";
        $yql_session = curl_init($yql_query_url);
        curl_setopt($yql_session, CURLOPT_RETURNTRANSFER,true);
        $yqlexec = curl_exec($yql_session);
        $yql_json =  json_decode($yqlexec,true);
        $currency_output = (float) $currency_input*$yql_json['query']['results']['rate']['Rate'];
        return $currency_output;
    }

    $payu = new payu();
    if (!$cookie->isLogged(true))
        Tools::redirect('authentication.php?back=order.php');
    elseif (!$cart->getOrderTotal(true, Cart::BOTH))
        Tools::displayError('Error: Empty cart');

    if ($cart->id_customer == 0 OR $cart->id_address_delivery == 0 OR $cart->id_address_invoice == 0 OR !$payu->active)
        Tools::redirectLink(__PS_BASE_URI__.'order.php?step=1');

    // Prepare payment

    $customer = new Customer((int)$cart->id_customer);

    if (!Validate::isLoadedObject($customer))
        Tools::redirectLink(__PS_BASE_URI__.'order.php?step=1');

    $currency = new Currency(Tools::getValue('currency_payement', false) ? Tools::getValue('currency_payement') : $cookie->id_currency);
    //id_currency == 2 => Currency = INR; do not convert
    if ($cookie->id_currency == 2)
        $total = (float)($cart->getOrderTotal(true, Cart::BOTH));
    #id_currency == 3 => Currency = EUR; convert
    elseif ($cookie->id_currency == 3) {
        $from = "EUR";
        $to = "INR";
        $amt = (float)($cart->getOrderTotal(true, Cart::BOTH));
        $total = (float) currencyConverter($from, $to, $amt);
    }
    #id_currency == 1 => Currency = USD; convert
    else {
        $from = "USD";
        $to = "INR";
        $amt = (float) ($cart->getOrderTotal(true, Cart::BOTH));
        $total = (float) currencyConverter($from, $to, $amt);
    }

    $key=Configuration::get('PAYU_MERCHANT_ID');
    $salt=Configuration::get('PAYU_SALT');
    $mode=Configuration::get('PAYU_MODE');
    $log=Configuration::get('PAYU_LOGS');


    $customer = new Customer((int)($cart->id_customer));

    $action='http://ift.tt/1eQdIkd';

    //$cart = new Cart((int)($cookie->id_cart));;
    $orderId = (int)($cookie->id_cart);

    //echo "<br/>id_order:" . $id_order;

    $txnid= $orderId+232585630456;
    $amount=$total;
    $productInfo='PayUMoney product information';
    $firstname=$customer->firstname;
    $Lastname= $customer->lastname;
    $deloveryAddress = new Address((int)($cart->id_address_delivery));
    $service_provider='payu_paisa';


    $Zipcode      =  $deloveryAddress->postcode;
    $email=$customer->email;
    $phone=$deloveryAddress->phone_mobile;

    if($mode=='real') {
          $action='http://ift.tt/1Fi5l9v';
    }

    $request=$key.'|'.$txnid.'|'.$amount.'|'.$productInfo.'|'.$firstname.'|'.$email.'|||||||||||'.$salt;
    //echo $request;
    //die();
    $Hash=hash('sha512', $key.'|'.$txnid.'|'.$amount.'|'.$productInfo.'|'.$firstname.'|'.$email.'|||||||||||'.$salt); 

    $baseUrl=Tools::getShopDomain(true, true).__PS_BASE_URI__;        

    if($log==1) {
        $query="insert into ps_payu_order(id_order,payment_request) values($orderId,'$request')";
        Db::getInstance()->Execute($query);
    }

    $surl=$baseUrl.'modules/'.'payu'.'/success.php'; 
    $curl=$baseUrl.'modules/'.'payu'.'/cancel.php?id='.base64_encode($orderId); 
    $furl=$baseUrl.'modules/'.'payu'.'/failure.php';    
    $Pg='CC';

    $payuInfo=array('action' => $action,
                    'key' => $key,
                    'txnid' => $txnid,
                    'amount' => $amount,
                    'productinfo' => $productInfo,
                    'firstname' => $firstname,
                    'Lastname' => $Lastname,
                    'Zipcode' => $Zipcode,
                    'email' => $email,
                    'phone' => $phone,
                    'surl' => $surl,
                    'furl' => $furl,
                    'curl' => $curl,
                    'Hash' => $Hash,
                    'Pg' => $Pg            
                    //'service_provider' => $service_provider
        );


    $smarty->assign('Message','Please wait, you will be redirected to PayU Checkout');
    $smarty->assign($payuInfo); 
    $smarty->display('payment.tpl');


        //$payu->display(__FILE__, 'payu.tpl');
    echo '<br/><br/>Please wait. We are processing your request<form action="'.$action.'" method="post" id="payu_form" name="payu_form" >
        <input type="hidden" name="key" value="'.$key.'" />
        <input type="hidden" name="txnid" value="'.$txnid.'" />
        <input type="hidden" name="amount" value="'.$amount.'" />
        <input type="hidden" name="productinfo" value="PayUMoney product information" />
        <input type="hidden" name="firstname" value="'.$firstname.'" />
        <input type="hidden" name="Lastname" value="'.$Lastname.'" />
        <input type="hidden" name="Zipcode" value="'.$Zipcode.'" />
        <input type="hidden" name="email" value="'.$email.'" />
        <input type="hidden" name="phone" value="'.$phone.'" />
        <input type="hidden" name="surl" value="'.$surl.'" />
        <input type="hidden" name="furl" value="'.$furl.'" />
        <input type="hidden" name="curl" value="'.$curl.'" />
        <input type="hidden" name="Hash" value="'.$Hash.'" />
        <input type="hidden" name="Pg" value="'.$Pg.'" />
        <input type="hidden" name="service_provider" value="'.$service_provider.'" />            

        </form> 

        <script type="text/javascript">

        setTimeout(document.payu_form.submit(),5000)

        </script>';
//$payu->validateOrder((int)$cart->id, Configuration::get('PS_OS_PREPARATION'), $total, $payu->displayName, NULL, NULL, (int)$currency->id, false, $customer->secure_key);

//$order = new Order($payu->currentOrder);
//echo $payu->currentOrder;
//Tools::redirectLink(__PS_BASE_URI__.'order-confirmation.php?id_cart='.(int)$cart->id.'&id_module='.$payu->id.'&id_order='.$payu->currentOrder.'&key='.$customer->secure_key);
?>

via Chebli Mohamed