More Invoice API Updates

sample/invoice/UpdateInvoice.php

@@ -0,0 +1,31 @@
+<?php
+
+// # Update Invoice Sample
+// This sample code demonstrate how you can update
+// an invoice.
+
+/** @var Invoice $invoice */
+$invoice = require 'CreateInvoice.php';
+use PayPal\Api\Invoice;
+
+// ### Update Invoice
+// Lets update some information
+$invoice->setInvoiceDate("2014-11-16 PST");
+
+
+// For Sample Purposes Only.
+$request = clone $invoice;
+
+try {
+    // ### Update Invoice
+    // Update an invoice by calling the invoice->update() method
+    // with a valid ApiContext (See bootstrap.php for more on `ApiContext`)
+    $invoice->update($apiContext);
+} catch (Exception $ex) {
+    ResultPrinter::printError("Invoice Updated", "Invoice", null, $request, $ex);
+    exit(1);
+}
+
+ResultPrinter::printResult("Invoice Updated", "Invoice", $invoice->getId(), $request, $invoice);
+
+return $invoice;