category_save_pre

Hello!

I have a problem with my first plugin, because I don’t know, how the category_save_pre filter works.

The plugin should automatically select the category, if there is only one category. I know, there’s a setting for default_category, but I use another plugin, which exclude for certain users the default_category.

function chooseCategory($id)
{
	$cat = get_categories(array('hide_empty'=>FALSE));
	if (count($cat) == 1)
	{
		$id = $cat[0]->cat_ID;
	}
	return $id;
}
add_filter('category_save_pre', 'chooseCategory');

What kind of parameters do I get for chooseCategory and what should be returned by this function?

Thanks
crille