Payment gateway not deleting cache (Very Important)

[Designinfo]

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 .

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 attached file has the entire payment gateway along with the payment.php file where the modification for the conversion code ( From Yahoo Finance ) is added.

 

Please advise what should I change.

payment.php

PayUMoney_prestashop.zip

Edited August 4, 2015 by info99 (see edit history)