WordPress E-Commerce Module PayPal Express Checkout with Coupon Code

WP e-Commerce is a very popular open-source shopping cart plug-in for WordPress, it supports most of the major PayPal payment options include Express Checkout, Web Site Payment STD and Web site payment Pro.

The plug-in supports the coupon discount function as well, however, the shopping cart only sends the total amount after discount to the PayPal, there is no discount coupon and discount price information on the PayPal activities report at all.

In order to let sellers get more information on the transaction involved the promotion coupons , I have modified one of the function - CallShortcutExpressCheckout which under /web-content/plugins/wp-e-commerce/merchants/paypal_certified.php

function CallShortcutExpressCheckout( $paymentAmount, $currencyCodeType, $paymentType, $returnURL, $cancelURL) {
//added $wpc_cart the shopping cart object itself
global $wpdb, $wpsc_cart;
//------------------------------------------------------------------------------------------------------------------------------------
// Construct the parameter string that describes the SetExpressCheckout API call in the shortcut implementation
//exit($cancelURL);
$purchase_log = $wpdb->get_row("SELECT `id`,`billing_region` FROM `".WPSC_TABLE_PURCHASE_LOGS."` WHERE `sessionid`= '".$wpdb->escape($_SESSION['paypalexpresssessionid']) ."' LIMIT 1", ARRAY_A) ;
$usersql = "SELECT `".WPSC_TABLE_SUBMITED_FORM_DATA."`.value, `".WPSC_TABLE_CHECKOUT_FORMS."`.`name`, `".WPSC_TABLE_CHECKOUT_FORMS."`.`unique_name` FROM `".WPSC_TABLE_CHECKOUT_FORMS."` LEFT JOIN `".WPSC_TABLE_SUBMITED_FORM_DATA."` ON `".WPSC_TABLE_CHECKOUT_FORMS."`.id = `".WPSC_TABLE_SUBMITED_FORM_DATA."`.`form_id` WHERE  `".WPSC_TABLE_SUBMITED_FORM_DATA."`.`log_id`=".$purchase_log['id']." ORDER BY `".WPSC_TABLE_CHECKOUT_FORMS."`.`order`";
//exit($usersql);
$userinfo = $wpdb->get_results($usersql, ARRAY_A);
//  print("
".print_r($usersql,true)."
");
//  print("
".print_r($userinfo,true)."
");

$nvpstr="&Amt=". $paymentAmount;
$nvpstr = $nvpstr . "&PAYMENTACTION=" . $paymentType;
$nvpstr = $nvpstr . "&RETURNURL=" . $returnURL;
$nvpstr = $nvpstr . "&CANCELURL=" . $cancelURL;
$nvpstr = $nvpstr . "&CURRENCYCODE=" . $currencyCodeType;
// added following 3 lines to send description to PayPal
foreach($wpsc_cart->cart_items as $cart_item){
$nvpstr = $nvpstr . "&DESC=" . $cart_item->product_name . " w COUPON# " . $wpsc_cart->coupons_name . " DISCOUNT $" . "$wpsc_cart->coupons_amount";
}
$data = array();

The shopping cart object $wpsc_cart needs to be announced as global, then add the coupon code number and discount total at DESC parameter which will be passed to PayPal API as payment description. The example below shown the applied coupon code and the discount amount on the PayPal transaction report.

For PayPal Web Payment Standard you will need to modify paypal_multiple.php as following

//$data['item_name_'.$i] = "Your Shopping Cart";
$itemdesc = "Discount " . $wpsc_cart->coupons_name . " $" . $wpsc_cart->coupons_amount . " for ";
foreach($wpsc_cart->cart_items as $cart_item){
  $itemdesc = $itemdesc . $cart_item->product_name . " ";
  }
$data['item_name_'.$i] = $itemdesc;