/**
 * Monitor Instances Action Sample
 * Enables monitoring for a running instance.  
 * @param Amazon_EC2_Interface $service instance of Amazon_EC2_Interface
 * @param mixed $request Amazon_EC2_Model_MonitorInstances or array of parameters
 */
function invokeMonitorInstances(Amazon_EC2_Interface $service, $request)
{
    try {
        $response = $service->monitorInstances($request);
        echo "Service Response\n";
        echo "=============================================================================\n";
        echo "        MonitorInstancesResponse\n";
        if ($response->isSetResponseMetadata()) {
            echo "            ResponseMetadata\n";
            $responseMetadata = $response->getResponseMetadata();
            if ($responseMetadata->isSetRequestId()) {
                echo "                RequestId\n";
                echo "                    " . $responseMetadata->getRequestId() . "\n";
            }
        }
        if ($response->isSetMonitorInstancesResult()) {
            echo "            MonitorInstancesResult\n";
            $monitorInstancesResult = $response->getMonitorInstancesResult();
            $instanceMonitoringList = $monitorInstancesResult->getInstanceMonitoring();
            foreach ($instanceMonitoringList as $instanceMonitoring) {
                echo "                InstanceMonitoring\n";
                if ($instanceMonitoring->isSetInstanceId()) {
                    echo "                    InstanceId\n";
                    echo "                        " . $instanceMonitoring->getInstanceId() . "\n";
                }
                if ($instanceMonitoring->isSetMonitoring()) {
                    echo "                    Monitoring\n";
                    $monitoring = $instanceMonitoring->getMonitoring();
                    if ($monitoring->isSetMonitoringState()) {
                        echo "                        MonitoringState\n";
                        echo "                            " . $monitoring->getMonitoringState() . "\n";
                    }
                }
            }
        }
    } catch (Amazon_EC2_Exception $ex) {
        echo "Caught Exception: " . $ex->getMessage() . "\n";
        echo "Response Status Code: " . $ex->getStatusCode() . "\n";
        echo "Error Code: " . $ex->getErrorCode() . "\n";
        echo "Error Type: " . $ex->getErrorType() . "\n";
        echo "Request ID: " . $ex->getRequestId() . "\n";
        echo "XML: " . $ex->getXML() . "\n";
    }
}