Magento filter product collection by multiple categories

Question

Is there an easy way to filter a product collection by multiple categories? To get all items in any of the listed categories? addCategoryFilter doesn't seem to allow an array.

Is the only way to get the collections for each category of interest separately then merge them?

I understand it used to be possible with something like

addAttributeToFilter('category_ids',array('finset'=>array('1','2')))

or similar, but that this is no longer possible since 1.4.

Note: I am using 1.6, and in case it's of any use, I'm using something like this:

$product = Mage::getModel('catalog/product');
$_productCollection = $product->getCollection()
  ->addAttributeToSelect('*')
  ->addAttributeToFilter('status',1)
  ->addStoreFilter();

Answer 1

Here's a method that doesn't require modifications to core. It's taken from this post with the addition of the 'group' clause to handle duplicate product records.

$categories = array(7,45,233);

        $collection = Mage::getModel('catalog/product')->getCollection()
            ->addAttributeToSelect('*')
            ->joinField('category_id',
                'catalog/category_product',
                'category_id',
                'product_id=entity_id',
                null,
                'left')
            ->addAttributeToFilter('category_id', array('in' => $categories));
        $collection->getSelect()->group('e.entity_id');

Answer 2

The way Magento works now, is to get the Store, and on the store, you can get the categories from the storecollection like $oStoreCollection->addCategoryFilter(array('1','2'));

I came across a solution that might help you, found here at:

http://www.magentocommerce.com/boards/&/viewthread/201114/#t329230

The code they use, looks like this: Override Mage/Catalog/Model/Resource/Eav/Mysql4/Product/Collection, and add the following methods:

public function addCategoriesFilter($categories)
    {
        $this->_productLimitationFilters['category_ids'] = $categories;

        if ($this->getStoreId() == Mage_Core_Model_App::ADMIN_STORE_ID) {
            $this->_applyZeroStoreProductLimitations();
        } else {
            $this->_applyProductLimitations();
        }

        return $this;
    }

    protected function _applyProductLimitations()
    {
        $this->_prepareProductLimitationFilters();
        $this->_productLimitationJoinWebsite();
        $this->_productLimitationJoinPrice();
        $filters = $this->_productLimitationFilters;

        // Addition: support for filtering multiple categories.
        if (!isset($filters['category_id']) && !isset($filters['category_ids']) && !isset($filters['visibility'])) {
            return $this;
        }

        $conditions = array(
            'cat_index.product_id=e.entity_id',
            $this->getConnection()->quoteInto('cat_index.store_id=?', $filters['store_id'])
        );
        if (isset($filters['visibility']) && !isset($filters['store_table'])) {
            $conditions[] = $this->getConnection()
                ->quoteInto('cat_index.visibility IN(?)', $filters['visibility']);
        }

        // Addition: support for filtering multiple categories.
        if (!isset($filters['category_ids'])) {
             $conditions[] = $this->getConnection()
                ->quoteInto('cat_index.category_id=?', $filters['category_id']);
            if (isset($filters['category_is_anchor'])) {
                $conditions[] = $this->getConnection()
                    ->quoteInto('cat_index.is_parent=?', $filters['category_is_anchor']);
            }
        } else {
            $conditions[] = $this->getConnection()->quoteInto('cat_index.category_id IN(' . implode(',', $filters['category_ids']) . ')', "");
        }

        $joinCond = join(' AND ', $conditions);
        $fromPart = $this->getSelect()->getPart(Zend_Db_Select::FROM);
        if (isset($fromPart['cat_index'])) {
            $fromPart['cat_index']['joinCondition'] = $joinCond;
            $this->getSelect()->setPart(Zend_Db_Select::FROM, $fromPart);
        }
        else {
            $this->getSelect()->join(
                array('cat_index' => $this->getTable('catalog/category_product_index')),
                $joinCond,
                array('cat_index_position' => 'position')
            );
        }

        $this->_productLimitationJoinStore();

        Mage::dispatchEvent('catalog_product_collection_apply_limitations_after', array(
            'collection'    => $this
        ));

        return $this;
    }

    protected function _applyZeroStoreProductLimitations()
    {
        $filters = $this->_productLimitationFilters;

        // Addition: supprot for filtering multiple categories.
        $categoryCondition = null;
        if (!isset($filters['category_ids'])) {
            $categoryCondition = $this->getConnection()->quoteInto('cat_pro.category_id=?', $filters['category_id']);
        } else {
            $categoryCondition = $this->getConnection()->quoteInto('cat_pro.category_id IN(' . implode(',', $filters['category_ids']) . ')', "");
        }

        $conditions = array(
            'cat_pro.product_id=e.entity_id',
            $categoryCondition
        );
        $joinCond = join(' AND ', $conditions);

        $fromPart = $this->getSelect()->getPart(Zend_Db_Select::FROM);
        if (isset($fromPart['cat_pro'])) {
            $fromPart['cat_pro']['joinCondition'] = $joinCond;
            $this->getSelect()->setPart(Zend_Db_Select::FROM, $fromPart);
        }
        else {
            $this->getSelect()->join(
                array('cat_pro' => $this->getTable('catalog/category_product')),
                $joinCond,
                array('cat_index_position' => 'position')
            );
        }

        return $this;
    }

It then gets called like this:

$collection = Mage::getModel('catalog/product')->getCollection()
                        ->addAttributeToSelect('*')
                        ->distinct(true) // THIS IS WHAT YOU NEED TO ADD
                        ->addCategoriesFilter($category->getAllChildren(true)); // Make sure you don't forget to retrieve your category here.

HTH