public function orderBy($column = '', $sort = 'desc')
    {
        $column=self::sanitize($column);
        $sort=strtoupper(self::sanitize($sort));

        /*check if the sort method passed is valid */
        if (!(hash_equals('DESC',$sort) || hash_equals('ASC',$sort))){
            static::$response["status"] = "error";
            static::$response["response"] = "The sort order in order by clause is invalid";
            static::$response['code'] = 6050;
            return static::terminate(static::$response);
        }

        if ($this->order == null) {
            $this->order = " ORDER BY $column $sort";
        } else {
            $this->order .= ", $column $sort";
        }
        return $this;
    }