How to make a PHP SOAP call to get sessionid

i am trying to connect to a webservice using php-soap . how can i create session with these parameter :

    `$client = new SoapClient("http://ift.tt/143MK45");
    var_dump($client->__getFunctions());

    $params = array(
            "AccountNumber" => "Myaccount",
            "UserName" => "myusername",
            "Password" => "mypass",
            "Target" => "Test"
    );

    $result = $client->__soapCall('CreateSession',$params);

    var_dump($result->CreateSessionResult);`

i used that code i got this :

array (size=21)

0 => string 'CreateSessionResponse CreateSession(CreateSession $parameters)' (length=62)

1 => string 'EndSessionResponse EndSession(EndSession $parameters)' (length=53)

2 => string 'AirLowFareSearchResponse AirLowFareSearch(AirLowFareSearch $parameters)' (length=71)

3 => string 'AirRevalidateResponse AirRevalidate(AirRevalidate $parameters)' (length=62)

4 => string 'BookFlightResponse BookFlight(BookFlight $parameters)' (length=53)

5 => string 'FareRulesResponse FareRules(FareRules $parameters)' (length=50)

6 => string 'CancelBookingResponse CancelBooking(CancelBooking $parameters)' (length=62)

7 => string 'TicketOrderResponse TicketOrder(TicketOrder $parameters)' (length=56)

8 => string 'TripDetailsResponse TripDetails(TripDetails $parameters)' (length=56)

9 => string 'AddBookingNotesResponse AddBookingNotes(AddBookingNotes $parameters)' (length=68)

10 => string 'MessageQueuesResponse MessageQueues(MessageQueues $parameters)' (length=62)

11 => string 'RemoveMessageQueuesResponse RemoveMessageQueues(RemoveMessageQueues $parameters)' (length=80)

12 => string 'AirSeatMapResponse AirSeatMap(AirSeatMap $parameters)' (length=53)

13 => string 'AirSeatReserveResponse AirSeatReserve(AirSeatReserve $parameters)' (length=65)

14 => string 'AirBookingDataResponse AirBookingData(AirBookingData $parameters)' (length=65)

15 => string 'MultiAirRevalidateResponse MultiAirRevalidate(MultiAirRevalidate $parameters)' (length=77)

16 => string 'MultiAirBookFlightResponse MultiAirBookFlight(MultiAirBookFlight $parameters)' (length=77)

17 => string 'IntelliFareSearchResponse IntelliFareSearch(IntelliFareSearch $parameters)' (length=74)

18 => string 'IntelliBestBuyResponse IntelliBestBuy(IntelliBestBuy $parameters)' (length=65)

19 => string 'AirQuoteResponse AirQuote(AirQuote $parameters)' (length=47)

20 => string 'FareRules1_1Response FareRules1_1(FareRules1_1 $parameters)' (length=59)

( ! ) Fatal error: SOAP Fault: (faultcode: VersionMismatch, faultstring: Wrong Version) in C:\wamp\www\wsdl.php on line 39

|| Time || Memory || Function || Location

1 || 0.0022 || 248904 || {main}( ) || ..\wsdl.php:0

2 || 9.3651 || 842608 || trigger_error ( ) || ..\wsdl.php:39

what is wrong with my code?