Use this filter in conjunction with the <model>_browse_sql hook to display what search filters are being applied to the item search.
If your plugin uses item_browse_sql to provide an additional filter when searching, you should use this filter to display the results.
Look through the request_array passed in the arguments for the key/value pair with key matching the additional filter you have created. Add the display value to the array as a new key/value pair, with the key being the name of your filter and the value being the text to display.
The MultiCollections plugin clobbers the core collection filtering message by checking if a multi-collection value is among the $_GET parameters and displaying the collection name.
public function filterItemSearchFilters($displayArray, $args)
{
$request_array = $args['request_array'];
if(isset($request_array['multi-collection'])) {
$db = get_db();
$collection = $db->getTable('Collection')->find($request_array['multi-collection']);
$displayValue = strip_formatting(metadata($collection, array('Dublin Core', 'Title')));
$displayArray['collection'] = $displayValue;
}
return $displayArray;
}