Create Order with nav web service in PHP

Hi.

I need to create a order from PHP using web service. I use the next code but I get this error:

Fatal error: Uncaught SoapFault exception: [a:Microsoft.Dynamics.Nav.Types.Exceptions.NavCSideException] The Sales Line already exists. Identification fields and values: Document Type='Order',Document No.='PV091/0040388',Line No.='10000' in C:\wamp\www\soap\navcreaped.php:228 Stack trace: #0 C:\wamp\www\soap\navcreaped.php(228): SoapClient->__call('Update', Array) #1 C:\wamp\www\soap\navcreaped.php(228): NTLMSoapClient->Update(Object(stdClass)) #2 {main} thrown in C:\wamp\www\soap\navcreaped.php on line 228

If I don't create order lines, I could save the new order but I can't create the order lines. I use the page 42 Sales_Order. Is posible to do using page 42 and 46 Sales_Line ?.

My code:

$pageURL = $baseURL.'Page/Sales_Order';

$service = new NTLMSoapClient($pageURL);

$create = new stdClass();

$sq = new stdClass();        

$create->Sales_Order = $sq;

$result = $service->create($create);

$key = $result->Sales_Order->Key;

echo $key;

$update = new stdClass();

$sq->Key = $key;

$sq->Sell_to_Customer_No = '000851';

$salesLineList = new stdClass();

$salesLine = new stdClass();

$salesLine->No = 'VIWE1102218';

$salesLine->Type = 'Item';

$salesLine->Quantity = 1;

$salesLine->Unit_Price = 101;

$salesLineList->Sales_Order_Line = $salesLine;

$sq->SalesLines = $salesLineList;

$update->Sales_Order = $sq;

$result = $service->Update($update);

THANKS!!