从XRMServices/2011/Organization.svc获取标识符有问题

我有一些代码类似于下面的Jason Lattimer的工作，但现在失败了。我可以在wsdl中找到"标识符"了。有人能提供帮助吗?

function GetADFS($url) {
    $ch = curl_init ();
    curl_setopt ( $ch, CURLOPT_URL, $url . "XrmServices/2011/Organization.svc?wsdl=wsdl0" );
    curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, 1 );
    curl_setopt ( $ch, CURLOPT_TIMEOUT, 60 );
    curl_setopt ( $ch, CURLOPT_SSL_VERIFYPEER, false );
    $response = curl_exec ( $ch );
    curl_close ( $ch );
    $responsedom = new DomDocument ();
    $responsedom->loadXML ( $response );
    // **************************************************       
    // **************************************************
    // Can no longer find this Identifier
    // **************************************************
    // **************************************************
    $identifiers = $responsedom->getElementsbyTagName ( "Identifier" );
    $identifier = $identifiers->item ( 0 )->textContent;
    return str_replace ( "http://", "https://", $identifier );
}