DataObject setFrom() problem

Hi, I have problem during using the DataObjects->setFrom() function. I can use it to copy data from an Array like $person->setFrom($_POST); However, when I want to copy from another object, nothing happened. My coding is: $productB = new DataObjects_Product; $productB->get($productid); $product = new DataObjects_Product; $product->setFrom($productB); $id = $product->insert(); The result is $product returns a blank DataObjects_Product without any data from $productB, am I using it right? Cheers, William