This question already has an answer here:
this post gives me a good idea of the basic approach of filters:
However, products have a custom attribute that is actually going to be stored as a multiselect element (which I assume is treated as an array):
$product->setAttribute('schoolid','11,12,13,18'); //the schoolid attribute for a given product //or perhaps it's stored as an array $product->setAttribute('schoolid', array(11,12,13,13));
this needs to be compared against a user's value so a this won't really work:
as this is more of an array comparison. Is there a standardized way to do this in Magento? Is there any way in other words to convert the product attribute to an array and do an in-array comparison within the existing model?