private function where($where) {
        if(is_array($where) && !empty($where)) {
            $wherefields = array();
            foreach($where as $field => $value) {
                $wherefields[] = $this->formatValues($field, $value);
            }
            if(!empty($wherefields)) {
                return " WHERE ".implode(' AND ', $wherefields);
            }
        }
        return false;
    }