how can i display only 1 value of an xml output received from an API?

I am learning how to work with an API. :D

Here is my code :

<?php

 $url = "http://ift.tt/1uvCzvZ"; # URL to WHMCS API file
 $username = "API_User"; # Admin username goes here
 $password = "XXXXXXXXXXXXXXX"; # Admin password goes here
 $postfields["username"] = $username;
 $postfields["password"] = md5($password);   
 $postfields["action"] = "validatelogin";
 $postfields["email"] = "my@email.com";
 $postfields["password2"] = "XXXXXXXXXXXX";
 $postfields["action"] = "getclientsproducts";
 $postfields["clientid"] = "9999";

 $query_string = "";
 foreach ($postfields AS $k=>$v) $query_string .= "$k=".urlencode($v)."&";

 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL, $url);
 curl_setopt($ch, CURLOPT_POST, 1);
 curl_setopt($ch, CURLOPT_TIMEOUT, 30);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ch, CURLOPT_POSTFIELDS, $query_string);
 curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
 $jsondata = curl_exec($ch);
 if (curl_error($ch)) die("Connection Error: ".curl_errno($ch).' - '.curl_error($ch));
 curl_close($ch);

 $arr = json_decode($jsondata); # Decode JSON String

$jsondata->$output;

 header('Content-type: text/plain');
 print_r($jsondata); # Output XML Response as Array

it does return something like this :

 <?xml version="1.0" encoding="utf-8"?>
<whmcsapi version="5.3.9">
<action>getclientsproducts</action>
<result>success</result>
<clientid>999</clientid>
<serviceid></serviceid>
<pid></pid>
<domain></domain>
<totalresults>1</totalresults>
<startnumber>0</startnumber>
<numreturned>1</numreturned>
<products>
<product>
<id>771</id>
<clientid>999</clientid>
<orderid>1342</orderid>
<pid>157</pid>
<regdate>2014-08-18</regdate>
<name>name</name>
<groupname>groupname</groupname>
<domain>hostname.com</domain>
<dedicatedip></dedicatedip>
</product>
</products>
</whmcsapi>
<id>999</id>
<clientid>888</clientid>
<orderid>1452</orderid>
<pid>193</pid>
<regdate>2014-08-18</regdate>
<name>NAME</name>
[...]

****Now my question is :

I would like to display only the value of what's between <domain> and </domain>

How can i do this?

Thank you