使用PHP和SOAP访问Bing翻译服务

有人知道如何使用PHP和SOAP访问Bing翻译服务(搜索api 2.0)吗?我尝试了不同的方法，但都没有成功。下面是我的代码:

$soap=new SoapClient("http://api.search.live.net/search.wsdl");//"http://schemas.microsoft.com/LiveSearch/2008/03/Search"
        $params["AppId"]="";
        $params["Query"]=$term;
        $params["SourceLanguage"]=$lang_from;
        $params["TargetLanguage"]=$lang_to;
        $params["Sources"]="Translation";
        //$params["Translation"]=array(
          //"Translation"=>array(
            //"SourceLanguage"=>$lang_from,
            //"TargetLanguage"=>$lang_to
          //)
        //);
        //$params["Sources"]=$sources;
        //$params["definitions"]="";
        //$res=$soap->Search(array("parameters"=>$params));
        die(print_r($soap->Search(array("parameters"=>$params))));