If you use the "keyword" search type it will allow you to select multiple columns in the UI. The correct code would be something like:
$searchWADAtbl_product_WADbSearch1->setSearch(array("type"=>"Edit", "comparison"=>"Includes", "join"=>"AND"), array("fld_p_name", "fld_p_descrption", "fld_p_collection", "fld_p_manufacturer"), "s", "fld_p_name");