Updates to Samples

- Added Sample to update payment amount just before execute
- Minor Docs Updates

sample/payments/ExecutePayment.php

@@ -11,9 +11,12 @@
 // API used: POST '/v1/payments/payment/<payment-id>/execute'.
 
 require __DIR__ . '/../bootstrap.php';
+use PayPal\Api\Amount;
+use PayPal\Api\Details;
 use PayPal\Api\ExecutePayment;
 use PayPal\Api\Payment;
 use PayPal\Api\PaymentExecution;
+use PayPal\Api\Transaction;
 
 // ### Approval Status
 // Determine if the user approved the payment or not
@@ -33,6 +36,27 @@ if (isset($_GET['success']) && $_GET['success'] == 'true') {
     $execution = new PaymentExecution();
     $execution->setPayerId($_GET['PayerID']);
 
+    // ### Optional Changes to Amount
+    // If you wish to update the amount that you wish to charge the customer,
+    // based on the shipping address or any other reason, you could
+    // do that by passing the transaction object with just `amount` field in it.
+    // Here is the example on how we changed the shipping to $1 more than before.
+    $transaction = new Transaction();
+    $amount = new Amount();
+    $details = new Details();
+
+    $details->setShipping(2.2)
+        ->setTax(1.3)
+        ->setSubtotal(17.50);
+
+    $amount->setCurrency('USD');
+    $amount->setTotal(21);
+    $amount->setDetails($details);
+    $transaction->setAmount($amount);
+
+    // Add the above transaction object inside our Execution object.
+    $execution->addTransaction($transaction);
+
     try {
         // Execute the payment
         // (See bootstrap.php for more on `ApiContext`)