Php,通过htaccess或Explode数组URL重写URL

This is my first question around here, so I'll try to be descriptive and everything.

Basically, I want to make a directory structre URL, Like accessories/watch/gold.

Now, I got three $_GET variables in my file, one for the accessories one for the watch and one for the color.

How can I make a rewrite that I will be able to get into the page just with accessories OR accessories/watch? It's all via the same FILE. Now, I have tried exploding the URL since i didn't knew how to make this regExp.

But, when I explode the URL I can INSERT as many slashes as I want into the url like this accessories////////watch////gold//, and I want with each word just one slash.

When I tried rewriting, basically it requried all three variables, and one time it didn't but made all the others just empty. I don't want them to be isset. Thanks!