Category-only Sidebar links (WordPress as a CMS)

Hello,

I am using wordpress as a basic cms for a new site: https://cafefoundation.org/wp/ In doing so I am using categories as sections, where $cat 1 might be NEWS, etc. All is great except…

The sidebar does not obey the $cat rules. The sidebar is quite simple, it is supposed to list the posts in a specific category, and does so just fine when archive.php is invoked, but breaks once single.php is used. No matter what I do I can’t get the sidebar to display the correct category permalinks in single.php. Here is my sidebar code:

<?php $posts = get_posts('category='.$cat); foreach($posts as $post):?>

<li><a href="<?php the_permalink()?>&cat=<?php echo $cat ?>"><?php the_title(); ?></a></li>

<?php endforeach; ?>

As you can see in this current iteration I am trying to pass $cat as a php variable to the next page, which does not work. You can see $cat echoed just beneath the header.

This is killing me, everything else works except this.