Functions from derived classes should be compatible with parent class.
So VW_Search_SearchController:: process_keywords_filters should have same params list.
Check in VW_Search_SearchController:: process_keywords_filters if there is variable $allow_ip_search used. If not you can change to
Code:
VW_Search_SearchController::
process_keywords_filters($user, $criteria, $allow_ip_search = false)
without a problem (it is an unused param, not nice, but possible).