SOAP V2 : catalog_category.tree Not Working on Localhost

Question

Configuration :

Code:

<?php
$proxy = new SoapClient('http://192.168.1.89/abc/api/v2_soap/?wsdl'); // TODO : change url
$sessionId = $proxy->login('cat', 'welcome'); // TODO : change login and pwd if necessary
$result = $proxy->catalogCategoryTree($sessionId);
var_dump($result);
?>

output:

Note : Localhost - Wamp 3.1 - Windows 7