Fixes to Agreement Search Transaction TimeStamp Parameter

- Updated TimeUpdate parameter to TimeStamp
- Updated Tests accordingly.
- Updated Samples accordingly
- Fixes #221

sample/billing/SearchBillingTransactions.php

@@ -6,19 +6,25 @@
 // https://developer.paypal.com/webapps/developer/docs/api/#search-for-transactions
 // API used: GET /v1/payments/billing-agreements/<Agreement-Id>/transactions? start-date=yyyy-mm-dd&end-date=yyyy-mm-dd
 
-// Retrieving the Agreement object from Create Agreement From Credit Card Sample
+// Retrieving the Agreement object from Get Billing Agreement. This may not be necessary if you are trying to search for transactions of already created Agreement.
 /** @var Agreement $agreement */
 $agreement = require 'GetBillingAgreement.php';
+
+// Replace this with your AgreementId to search transactions based on your agreement.
 $agreementId = $agreement->getId();
+
 use PayPal\Api\Agreement;
 
+// Adding Params to search transaction within a given time frame.
+$params = array('start_date' => date('Y-m-d', strtotime('-15 years')), 'end_date' => date('Y-m-d', strtotime('+5 days')));
+
 try {
-    $result = Agreement::searchTransactions($agreementId,array('start_date' => '2013-01-01', 'end_date' => '2015-01-20'), $apiContext);
+    $result = Agreement::searchTransactions($agreementId, $params, $apiContext);
 } catch (Exception $ex) {
     ResultPrinter::printError("Search for Transactions", "AgreementTransaction", $agreementId, null, $ex);
     exit(1);
 }
 
-ResultPrinter::printResult("Search for Transactions", "AgreementTransaction", $agreementId, null, $result);
+ResultPrinter::printResult("Search for Transactions", "AgreementTransaction", $agreementId, $params, $result);
 
 return $agreement;