Order API Support

- Added Order API Support
- Updated Sample Code to demonstrate
- Updated Sample Docs
- Fixes #237

sample/payments/OrderDoVoid.php

@@ -0,0 +1,40 @@
+<?php
+// #Void Order Sample
+// Use this call to void an existing order.
+// Note: An order cannot be voided if payment has already been partially or fully captured.
+// API used: POST /v1/payments/orders/<Order-Id>/do-void
+
+/** @var \PayPal\Api\Payment $payment */
+$payment = require __DIR__ . '/ExecutePayment.php';
+
+use PayPal\Api\Capture;
+use PayPal\Api\Amount;
+
+// ### Approval Status
+// Determine if the user approved the payment or not
+if (isset($_GET['success']) && $_GET['success'] == 'true') {
+
+    // ### Retrieve the order
+    // OrderId could be retrieved by parsing the object inside related_resources.
+    $transactions = $payment->getTransactions();
+    $transaction = $transactions[0];
+    $relatedResources = $transaction->getRelatedResources();
+    $relatedResource = $relatedResources[0];
+    $order = $relatedResource->getOrder();
+
+    try {
+        // ### Void Order
+        // Call void method on order object. You will get an Order Object back
+        $result = $order->void($apiContext);
+        ResultPrinter::printResult("Voided Order", "Order", $result->getId(), null, $result);
+    } catch (Exception $ex) {
+        ResultPrinter::printError("Voided Order", "Order", null, null, $ex);
+        exit(1);
+    }
+
+    return $result;
+
+} else {
+    ResultPrinter::printResult("User Cancelled the Approval", null);
+    exit;
+}