未捕获的SoapFault异常：会话已过期（在Magento 1.9.x SOAP v2中）

Question

I'm trying to access Magento Core API through PHP SoapClient, but I am having the session login issue described below.

Uncaught SoapFault exception: Session expired

In SoapUI it works fine, the problem is on PHP call. Call code below:

ini_set("soap.wsdl_cache_enabled", 0);
ini_set("soap.wsdl_cache", 0);
ini_set("error_reporting", -1);
ini_set("display_errors", 'On');
$store_url = 'http://myMagentoUrl/';
$wsdl_url = $store_url . 'api/v2_soap/?wsdl';
$api_user = 'user';
$api_key = 'pass';
$proxy = new SoapClient($wsdl_url);
$sessionId = $proxy->login(['username'=>$api_user, 'apiKey'=>$api_key]);
$result = $proxy->salesOrderList($sessionId->result);
echo'<pre>';
print_r($result) ;
echo '</pre>';