How can I show the post thumbnail from the most recent of a certain post type, in widget?

Question

I'm using the excellent PHP Code Widget plugin, and want to create a widget that displays the post thumbnail (aka featured image) for the most recent 'project' post. Here's the code I have so far, but it isn't producing the desired result. This actually outputs nothing.

<?php
global $post;
$args = array(
    'post_type' => 'project',
    'posts_per_page' => 1,
    ); 
$thumbnails = get_posts($args);
foreach ($thumbnails as $post)
{
    setup_postdata($post);
        ?>
        <a href="<?php the_permalink(); ?>"><?php the_post_thumbnail( 'thumbnail' ); ?></a>
        <?php 
        }

Any suggestions on what I need to change for this to work?

Answer 1

Moving here so comments don't turn into a mess.

Basically there are two things that can go wrong here:

1. Fetching of posts. Check that $thumbnails gets correct post and only one. I am not sure if that is the issue, but get_posts() docs list numberposts argument instead of posts_per_page that is listed for query_posts(). That might make a difference.

2. Messing with global variables. For this usage I wouldn't touch global $post at all, directly or with setup_postdata() either. Just use non-loop versions of functions that can fetch things you need by post id - get_permalink() and get_the_post_thumbnail().