WSDL using soapclient

Need to access a webservice using soapclient.I have the following settings.

ini_set('default_socket_timeout', 120);
$client = new SoapC开发者_如何学Client(
  "http://example.com/OnlineOrderProcessingWS.asmx?WSDL",
  array('proxy_host'    => "proxy url",
        'proxy_port'    => proxy port
  )
);
$param=array("varname1"=>'value1',"varname2"=>'value2');

$result = $client->CustomerOrder($param);
print_r($result); 

Executing this script throwing

Fatal error: Uncaught SoapFault exception: [HTTP] Error Fetching http headers.

The most common reason for this error seems to be a timeout while waiting on the service response. You already adjust your socket_timeout to 120, but might want to try an even higher value. How long does it take for the error to be returned?