public function tostring()
    {

        if (empty($this->value)) {

            return (empty($this->function)) ? "$this->function(`$this->name`)" : " `$this->name`";
        }

        $str = strtoupper($this->condition) . " `$this->name`";

        if (is_array($this->value)) {
            $str .= " IN (" . implode("','", $this->value) . "')";
        } else {
            $str .= " = '$this->value'";
        }

        return $str;
    }