I want to make some url rewrite 

```
http://www.domain.com/products/feed.php?keywords=*somewords*

```

=>

```
http://subdomain.domain.com/products/feed/*somewords*

```

I have set in htaccess

```
RewriteRule 301 products/feed.php?keywords=(.*?) http://subdomain.domain.com/products/feed/$2.xml

```

but it seens not working, how to make a right write? Thanks.