PHP stdClass中的可捕获致命错误

I have a problem in my code. After the code run, it rises this error:

Catchable fatal error: Object of class stdClass could not be converted to string in /home/1234/domains/1234.com/public_html/sender.php on line

The code is:

<?php
$r = array();
$num = array();
$num = split(",",$_REQUEST['num']);
$num_length = count($num);
$num_length--;

$userName="134";
$password="1234";
$domainName="1234.com";
$lineNumber="50001234";
$text=$_REQUEST['msg'];

date_default_timezone_set('Asia/Tehran');
$client= new SoapClient('http://91.98.100.94/service.asmx?WSDL');

$parameters['domain'] = $domainName;
$parameters['username'] = $userName;
$parameters['password'] = $password;
$parameters['srcNumber'] = $lineNumber;
$parameters['body'] = array($text);
$parameters['recipientnumbers'] = $_REQUEST['num'];

$r = $client->Send($parameters);

print (string) $r->SendResult;
?>