Unable to pass current category ID in paramter

Hi,

I am using some code to retrieve the current page’s category so that the sidebar displays all of the other posts from said category.

I have tested that my $catid retrieves the correct category id, and the HTML code posts fine when given an exact category id (i.e. 5). It is just when using a variable in the parameter of get_posts() that it does not seem to work.

Here is my current code:

<?php
if (is_category() || is_single()) { 

foreach((get_the_category()) as $cat) {
	$catid = $cat->cat_ID;
	$catname = $cat->cat_name;
}
$sidebarparam = 'numberposts=10&category=$catid';
?>
<ul>
   <?php
      $catposts = get_posts($sidebarparam);
      foreach($catposts as $post) :
   ?>
   <li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
   <?php endforeach; ?>
</ul>
} ?>

Any help would be appreciated!