Getting info from more than one category with the following code

Hi there,
I’ve been working at this for a while, and I just can’t figure it out.
I’m trying to post the titles from only certain categories on my sidebar.

So far, I can only do one at a time with this code:

‘<?php
$posts = get_posts(‘numberposts=5&offset=0&category=4’);
foreach($posts as $post) :?>’

Can anyone tell me how to post recent articles from more than that one cat?

Thanks,
Matt