Product Collection class in magento is Mage_Catalog_Model_Resource_Eav_Mysql4_Product_Collection.

Here is some Sort of code snippet for Magento Collection(s).

Get All Products of a category

$collection = Mage::getResourceModel(‘catalog/product_collection’)
->setStoreId($this->getStoreId())
->addCategoryFilter($category);

Tn this the addCategoryFilter() function, is used to get all products of a particular category. So, if you want to get all products of a certain category use this function.

Visibility Filter
———————
$collection = Mage::getResourceModel(‘catalog/product_collection’);
Mage::getSingleton(‘catalog/product_visibility’)
->addVisibleInCatalogFilterToCollection($collection);

The addVisibleFilterToCollection() adds visibility filter to a product collection i.e only products which are visible in frontend. The product which have “Not Visible Individually” selected in admin are removed.

Status Filter
—————–
$collection = Mage::getResourceModel(‘catalog/product_collection’);
Mage::getSingleton(‘catalog/product_status’)->addVisibleFilterToCollection($collection);

This basically filters out products which are “Disabled”. Only “Enabled” products remain in the collection.

Add Product Price To Collection
——————————————–
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection ->addMinimalPrice()
->addFinalPrice()
->addTaxPercents();

This adds the product prices, i.e base price, final price etc to the collection. Also, price after tax, if applicable.

Filter By Ids
—————–
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addIdFilter(array(1,2,3));
//$collection->addIdFilter(array(1,2,3),false);

This puts an id filter, only product with ids 1,2,3 remain in the collection. The function parameter is true/false, this means include/exclude products from collection.

Add Website ID to the collection
——————————————–
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addWebsiteNamesToResult();

This adds website_id of each product to that collection. Only useful when using multiple websites in magento.

Filter Current Store Products
—————————————
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addStoreFilter();

Filter Current Website Products
——————————————-
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addWebsiteFilter();

Get All Products Ids
—————————
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->getAllIds();

This returns an array with only products ids of collection.

Add SEO Product URL
——————————
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addUrlRewrite();

This adds SEO friends urls to our product collection.

Add Category Ids
————————
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addCategoryIds();

This will add category ids to the products.

Add Tier Pricing
————————
$collection = Mage::getResourceModel(‘catalog/product_collection’);
$collection->addTierPriceData();

This added tier pricing data to each product in the collection.While we are on this subject, let look at some important function of the Product Object as well.