public function enable($ver = null)
    {
        if ($ver == null) {
            $ver = ($this->getVersion())
                ?$this->getVersion()
                :$this->defVersion;
        }

        if ($this->isEnabled() && $this->getVersion() == $ver) {
            return $this;
        }

        $ver = (string) $ver;
        $this->enabled = $ver;

        return $this;
    }