code: public function getFulfillmentPreview($request)
      {
          if (!($request instanceof FBAOutboundServiceMWS_Model_GetFulfillmentPreviewRequest)) {
              $request = new FBAOutboundServiceMWS_Model_GetFulfillmentPreviewRequest($request);
          }
          $parameters = $request->toQueryParameterArray();
          $parameters['Action'] = 'GetFulfillmentPreview';
          $httpResponse = $this->_invoke($parameters);
  
          $response = FBAOutboundServiceMWS_Model_GetFulfillmentPreviewResponse::fromXML($httpResponse['ResponseBody']);
          $response->setResponseHeaderMetadata($httpResponse['ResponseHeaderMetadata']);
          return $response;
      }
docs: Get Fulfillment Preview
  Get estimated shipping dates and fees for all
  available shipping speed given a set of seller SKUs and quantities
  
  If "ShippingSpeedCategories" are inputed, only previews for those options will be returned.
  
  If "ShippingSpeedCategories" are not inputed, then previews for all available options
  are returned.
  
  The service will return the fulfillment estimates for a set of Seller
  SKUs and quantities.
  
  @param mixed $request array of parameters for FBAOutboundServiceMWS_Model_GetFulfillmentPreview request or FBAOutboundServiceMWS_Model_GetFulfillmentPreview object itself
  @see FBAOutboundServiceMWS_Model_GetFulfillmentPreviewRequest
  @return FBAOutboundServiceMWS_Model_GetFulfillmentPreviewResponse
  
  @throws FBAOutboundServiceMWS_Exception