public function values($values)
    {
        if (is_array($values) === true) {
            if (is_numeric(key($values)) === true) {
                $this->values = array(
                    null,
                    implode(', ', $values)
                );
            } else {
                $this->values = array('', '');
                foreach ($values as $key => $value) {
                    if (stripos($key, '.') !== false) {
                        $key = substr($key, stripos($key, '.') + 1);
                    }
                    $this->values[0] .= $key . ', ';
                    $this->values[1] .= $value . ', ';
                }
                $this->values[0] = substr($this->values[0], 0, -2);
                $this->values[1] = substr($this->values[1], 0, -2);
            }
        } else {
            $this->values = array(
                null,
                $values
            );
        }

        return $this;
    }