add feature to a webservice product

[agarmur]

Hello, I try to add a feature on a product with a webservice, but I have a problem, the function addFeaturesCustomToDB or addFeaturesToDB do not work.

Let me explain:
Here is the idea of my code:

$product = new Product();
$product->name = "test";
$product->price = 12;
$product->addFeaturesCustomToDB(12,(int)Configurateur::get('PS_LANG_DEFAULT'), "testFeature");

then i go to the backoffice of prestashop, and my product does not a features :