How to set selected value in multiselect attribute

Question

How to set selected value in multiselect attribute progmatically. I tried this one but it doesn't work for me.

How to Programmatically set a Product's Multi-Select Attribute by Labels

the code on the link above doesn't stop from loading

$productObj = Mage::getModel('catalog/product')->load($product->getId());
$productObj->setData('filter_category','51,52');
$productObj->save();    

the code above is invoke after catalog_product_save_after

Answer 1

Since you want to do this in the action catalog_product_save_after you could simple update the individual product attribute and not the complete product, thus stopping the infinite loop problem.

$attrCode = 'your_attribute';
$sourceModel = Mage::getModel('catalog/product')->getResource()
    ->getAttribute($attrCode)->getSource();
$valuesText = explode(',', 'red,green,blue');
$valuesIds = array_map(array($sourceModel, 'getOptionId'), $valuesText);
$product->setData($attrCode, $valuesIds);
$product->getResource()->saveAttribute($product, $attrCode);

Answer 2

As others have mentioned, the problem is that you go into an infinite loop if you save the product again in the save_after event.

1. you should use the save_before event
2. Don't load() the product again, $product already contains all data
3. Don't save() as the data you set on $product will be saved after the event has finished

So the code for your new observer looks like this:

public function setFilterCategoryBeforeSave(Varien_Event_Observer $observer)
{
    $observer->getProduct()->setData('filter_category','51,52');
}

That's all.

Answer 3

You can filter multiple select using finset. Below is a small example of how filter it

$collection = $this->getCollection()
            ->addAttributeToSelect('*')
            ->addAttributeToFilter('visibility', $visibility)
            ->addAttributeToFilter('status', Mage_Catalog_Model_Product_Status::STATUS_ENABLED)
            ->addAttributeToFilter($attribute,array('finset'=>array_search($selection,$valueId)))
            ->setPageSize($limit)
            ->load();
        Mage::getSingleton('cataloginventory/stock')->addInStockFilterToCollection($collection); 

here $selection is the value of multiple select attribute to be filtered