Gravity forms and wp_update_post [closed]

Looking at core, it seems post_category always overwrites:

 // Passed post category list overwrites existing category list if not empty.

Instead, try something like:

//wp_set_post_terms( $post_id, $terms, $taxonomy, $append )
wp_set_post_terms( $entry["post_id"], 48, $taxonomy, true )

Obviously, replace $taxonomy with the correct name.