Magento 1.6.1: type vs. type_id, categories vs. category_ids?

Question

They seem to bear the same value in the results returned by product.info API call. For example:

[type] => simple
[type_id] => simple


[categories] => Array
    (
        [0] => 4
    )
[category_ids] => Array
    (
        [0] => 4
    )

So which one of them am I supposed to use when creating or updating products? Or should I just stick to both of them and set the same value for both of them when creating or updating products?

Thanks!

Answer 1

The "id" values are what is stored in the database, their shorter equivalents are set by the product model for convenience and it is responsible for copying changes back to the "id" field. In theory you can use either interchangeably.