Magento addAttributeToFilter

Question

I'm using attributes to a product, availablepostalcodes. This is a multi-select, there are 3 options per product: 1234 2345 3456

Now after a post (form) on the categorypage i've $_POST['postalcode'], this contains 2345. But when i do this nothing will filter:

$_productCollection=$this->getLoadedProductCollection();
$_productCollection->addAttributeToFilter("availablepostalcodes", array("finset"=>"5021"));


echo $_productCollection->load()->count(); 

The echo still shows 5, however it should be 1, cause one product has that available postalcode.

This is the product-list view /catalog/product/list.phtml

What do i miss or don't see?

Edit:

$_productCollection = Mage::getModel('catalog/product')
                              ->getCollection()
                              ->addAttributeToSelect('availablepostalcodes')
                              ->addAttributeToFilter('entity_id', array('in' => $_productCollection->getAllIds()));  

Then i get all the products again.

But when i do $_productCollection->addAttributeToFilter("availablepostalcodes", array("in" => array(5021'))); it still doesn't work

Answer 1

you have a multiselect so you need to filter for the multiselect option id not the option value!

Answer 2

try in instead of finset

$_productCollection->addAttributeToFilter("availablepostalcodes", array("in"=>"5021"));