Filtering Magento product collection by multiple categories using AND condition

Question

I trying to display a list of products in Magento based on multiple categories. I'm using the following code which works well:

$collection = Mage::getModel('catalog/product')->getCollection() 
->addAttributeToSelect('id')
->addAttributeToSelect('sku')
->addAttributeToSelect('name')
->addAttributeToFilter('status', 1)
->addAttributeToFilter('visibility', 4)
->addStoreFilter();

$catfilters = "1981,1982,1983";  
$conditions = array(); 
foreach ($catfilters as $categoryId) {  
     if (is_numeric($categoryId)) {    
          $conditions[] = "{{table}}.category_id = $categoryId";  
     } 
}

$collection->distinct(true)
->joinField('category_id', 'catalog/category_product', null, 'product_id = entity_id', implode(" OR ", $conditions), 'inner');

This works well and lists all products with category 1981, 1982 and 1983. So far so good but I also would like to filter on a fourth category "1984" but this should be using an "AND" condition. In order words: (1981 OR 1982 OR 1983) AND (1984).

After having read up on it I believe I need to add another joinField but I'm not sure how it would be done. Any help would be really appreciated.

Answer 1

Haven't tested but maybe this will work:

$collection->distinct(true)
    ->joinField('category_id', 'catalog/category_product', null, 'product_id = entity_id', "(".implode(" OR ", $conditions).") AND ({{table}}.category_id = 1984)", 'inner');