Add products which have a catalog price rule to a specific category

Question

I got 11 different catalog price rules set up in my Magento 1.9.3 store and I've got a script randomly activating one of the price rules every day with a cronjob.

Now I want to add the products which have a catalog price rule activated to a specific category so I will have 'Day deals' which are randomly selected every day.

I'm no expert at all in coding but by googling I came up with this:

To clear the category of products first:

    <?php
require_once 'app/Mage.php';
Mage::app();

$category = Mage::getModel('catalog/category')->load(846);
$category->setPostedProducts(array());
$category->save();


?>

And to add the products in the category:

    <?php
require 'app/Mage.php';

$category_id = 846;
$resource = Mage::getSingleton('core/resource');
$connection = $resource->getConnection('core_read');
$tableName = $resource->getTableName('catalogrule_product');
$productIdList = $connection->fetchAll('SELECT product_id FROM '.$tableName.''); 


foreach ($productIdList as $productId) {
    $product = $productId['product_id'];

Mage::getSingleton('catalog/category_api')
            ->assignProduct($category_id,$product);
            }
            ?>

Unfortunately, it isn't working. What should I do to make this work?

** FIX UPDATE **

The second script needed

require_once 'app/Mage.php';

Answer 1

If you have a flat category enabled, then please disable it first and run that script again, the code which you have used will not work with flat category enabled. So after running the script enable flat catalog again and then do indexing.

Also You can try below code to assign product to any category by modifying your code:

foreach ($productIdList as $productId) {
$product = Mage::getModel("catalog/product")->load($productId);

$categories = $product->getCategoryIds();
$categories[] = $category_id;
$product->setCategoryIds($categories);
$product->save();
            }