php - F3 return query result -

i try build rest interface using fat free framework. use following code query database:

$product = new db\sql\mapper($this->db, 'product'); $product->load(array('id=?', $this->productid)); 

i can return instance title with

echo json_encode($product->title); 

but how return whole row? following won't work

echo json_encode($product); 

found it. had use

echo json_encode($product->cast());