Session data changed in php - php

Question

This is my code
class WcfClient {
public $wcfClient = null;
public $user = null;
public function __construct(){
if(isset($_SESSION['APIClient']) && $_SESSION['APIClient'] != null){
$this->wcfClient = $_SESSION['APIClient'];
}
}
public function __destruct(){
}
// Authanticate
private function Authenticate(){
global $_sogh_soapUrl, $_isDebug, $_sogh_header;
$wcargs = array();
$consumerAuthTicket = null;
if($this->wcfClient == null){
$args = array(
'clubname'=>'Wellness Institute at Seven Oaks',
'consumerName'=>'api',
'consumerPassword'=>'api'
);
try{
$wcargs = array(
'soap_version'=>SOAP_1_2
);
if($_isDebug){
$wcargs = array(
'soap_version'=>SOAP_1_2,
'proxy_host'=>"192.168.0.1",
'proxy_port'=>8080
);
}
// Connect to the API with soapclient
$soapAPIClient = new SoapClient($_sogh_soapUrl, $wcargs);
$response = $soapAPIClient->AuthenticateClubConsumer($args);
if(isset($response->AuthenticateClubConsumerResult)){
if(isset($response->AuthenticateClubConsumerResult->IsException) && $response->AuthenticateClubConsumerResult->IsException == true){
// some error occur
$this->wcfClient = null;
$_SESSION['APIClient'] = $this->wcfClient;
} else{
// set consumer ticket
$consumerAuthTicket = $response->AuthenticateClubConsumerResult->Value->AuthTicket;
// $loginData = $responseCode->ReturnValueOfConsumerLoginData;
$headers = array();
$headers[] = new SoapHeader($_sogh_header, "ConsumerAuthTicket", $consumerAuthTicket);
$soapAPIClient->__setSoapHeaders($headers);
// add to session
$this->wcfClient = $soapAPIClient;
$_SESSION['APIClient'] = $this->wcfClient;
}
}
} catch(SoapFault $fault){
$this->error('Fault: ' . $fault->faultcode . ' - ' . $fault->faultstring);
} catch(Exception $e){
$this->error('Error: ' . $e->getMessage());
}
}
return $this->wcfClient;
}
I store the soap client object in $_SESSION['APIClient'], but second times when run some data has been changed in session, I am use this class in drupal 7, I want to save the time using session, because authenticating takes long time.
Please help
Thank in advance