soap request with xml string parameter

May be there is few blog similar this but I can't solve the problem. I convert xml to string and try to pass it as a parameter. Then I got error. I try to slove it using cdata but it not solved my problem. At last I try to use SoapVar and getting following error

MY CODE:

$survey =   $domtree->saveXML();    
$soapVar = new SoapVar($survey,XSD_ANYXML); 
$params = array(>        
    "ManagerID" => 0,
    "Reg_SalesCenterID" => $id,
    "surveys" => $soapVar,
    "SalesCenterList" => $SalesCenter);

try {
    $response = $soapClient->__soapCall('AddNewContact', array($params));
}catch (SoapFault $fault) {
    echo 'Request : <br/><xmp>',
    $soapClient->__getLastRequest(),
    '</xmp><br/><br/> Error Message : <br/>',
    $fault->getMessage();
}

ERROR

The formatter threw an exception while trying to deserialize the message: Error in deserializing body of request message for operation 'AddNewContactBestRent'. No characters can appear before the XML declaration. Line 2, position 1385.