Index: payment/ps_paypal.php
@@ -260,7 +260,7 @@
 
     $fields = array(
         'charset' => $pp_charset,
-        'cmd' => "_ext-enter",
+        'cmd' => "_cart",
         'custom' => $order_secureid,
         'invoice' => $pp_ordr,
         'redirect_cmd' => '_xclick',
@@ -273,9 +273,10 @@
         'last_name' => $bill_lastname,
         'business' => $pp_acc,
         'amount' => $pp_total,
-        'tax_cart' => 0,
-        'shipping' => 0,
-        'handling' => 0,
+        'tax_cart' => func_paypal_convert_to_BasicAmountType($cart["tax_cost"], $pp_curr),
+        'shipping' => func_paypal_convert_to_BasicAmountType($cart["shipping_cost"], $pp_curr),
+        'handling_cart' => func_paypal_convert_to_BasicAmountType(($cart["need_giftwrap"] == 'Y' ? $cart["taxed_giftwrap_cost"] : 0), $pp_curr),
+        'discount_amount_cart' => func_paypal_convert_to_BasicAmountType($cart["giftcert_discount"] + $cart["discount"] + $cart["coupon_discount"], $pp_curr),
         'weight_cart' => 0,
         'currency_code' => $pp_curr,
         'return' => $_location."/payment/ps_paypal.php?mode=success&secureid=$order_secureid",
@@ -304,6 +305,39 @@
     if ($module_params['use_preauth'] == 'Y')
         $fields['paymentaction'] = 'authorization';
 
+    # NOTE: Updated, version (http://forum.x-cart.com/showthread.php?t=57734). No product quantity limitation.
+    #       The shipping cost for the whole order goes with the first product.
+    #       This has been done to avoid rounding problems at PayPal and keep correct totals.
+    $__pp_products_html = ""; $__pp_total_cost = 0; $__pp_counter = 1;
+    foreach ($cart['products'] as $__pp_product) {
+        $__pp_products_html .= "<input type=\"hidden\" name=\"item_name_$__pp_counter\" value=\"$__pp_counter. $__pp_product[product] ($__pp_product[productcode])\">";
+        $__pp_products_html .= "<input type=\"hidden\" name=\"quantity_$__pp_counter\" value=\"$__pp_product[amount]\">";
+        $__pp_products_html .= "<input type=\"hidden\" name=\"amount_$__pp_counter\" value=\"".func_paypal_convert_to_BasicAmountType($__pp_product['display_price'], $pp_curr)."\">";
+        $__pp_products_html .= "<input type=\"hidden\" name=\"shipping_$__pp_counter\" value=\"".func_paypal_convert_to_BasicAmountType(($__pp_counter == 1 ? $cart["shipping_cost"] : 0), $pp_curr)."\">\n";
+        $__pp_total_cost += func_paypal_convert_to_BasicAmountType($__pp_product['display_price'], $pp_curr) * func_paypal_convert_to_BasicAmountType($__pp_product['amount'], $pp_curr);
+        $__pp_counter++;
+    }
+
+    # Gift Certificate(s)
+    if (isset($cart['giftcerts']) && !empty($cart['giftcerts'])) {
+        foreach ($cart['giftcerts'] as $__cert) {
+            $__pp_products_html .= "<input type=\"hidden\"name=\"item_name_$__pp_counter\" value=\"$__pp_counter. ".func_get_langvar_by_name('lbl_gift_certificate', null, false, true)."\">";
+            $__pp_products_html .= "<input type=\"hidden\"name=\"quantity_$__pp_counter\" value=\"1\">";
+            $__pp_products_html .= "<input type=\"hidden\"name=\"amount_$__pp_counter\" value=\"".func_paypal_convert_to_BasicAmountType($__cert['amount'], $pp_curr)."\">";
+            $__pp_products_html .= "<input type=\"hidden\"name=\"shipping_$__pp_counter\" value=\"0\">";
+            $__pp_products_html .= "<input type=\"hidden\"name=\"handling_$__pp_counter\" value=\"0\">";
+            $__pp_products_html .= "<input type=\"hidden\"name=\"tax_$__pp_counter\" value=\"0\">\n";
+            $__pp_total_cost += func_paypal_convert_to_BasicAmountType($__cert['amount'], $pp_curr);
+            $__pp_counter++;
+        }
+    }
+
+    $fields['discount_amount_cart'] = abs(func_paypal_convert_to_BasicAmountType($fields['discount_amount_cart'] + ($pp_total - $__pp_total_cost - $fields['tax_cart'] - $fields['shipping'] - $fields['handling_cart'] - $fields['discount_amount_cart']), $pp_curr));
+
+    if ($__pp_products_html) {
+        $fields['ext_order_info_html'] = $__pp_products_html;
+    }
+
     x_load('user');
     $areas = func_get_profile_areas(empty($login) ? 'H' : 'C');
 
Index: skin/common_files/payments/payment_form.tpl
@@ -4,7 +4,11 @@
 *}
 <form method="{$method}" action="{$request_url|amp}" name="process">
 {foreach from=$fields key=fn item=fv}
-<input type="hidden" name="{$fn}" value="{$fv|escape:"html"}" />
+{if $fn eq "ext_order_info_html"}
+  {$fv}
+{else}
+  <input type="hidden" name="{$fn}" value="{$fv|escape:"html"}" />
+{/if}
 {/foreach}
 
 {if $autosubmit}