Associated category preview

<div class="thumbnails container_24">
	<!-- loop in thumbnails for the relevant category -->
	<?php
	// put all the category IDs of current post into an array
	$categories = get_the_category( $post->ID );
	$category_id_array = array();
	foreach ( $categories as $category ) {
		$category_id_array[] = $category->cat_ID;
	}

	// define how many thumbnails to show (at most)
	$thumbnail_max = 6;

	// grab all posts in the same categories as the current post
	$category_thumb_args = array( 'category__in' => $category_id_array, 'posts_per_page => $thumbnail_max', 'exclude' => $post->ID );
	$category_thumb_query = new WP_Query( $category_thumb_args );

	// if there are posts loop through them
	if ( $category_thumb_query->have_posts() ) :
		while($category_thumb_query->have_posts()) : $category_thumb_query->the_post(); ?>
			<?php if ( has_post_thumbnail() ) :?>
			<div class="grid_8 newsbox">
			<div class="news-thumbnail"><?php the_post_thumbnail(); ?></div>
			<div class="news-description">
			<a class="news-link" href="<?php the_permalink() ?>" rel="<?php the_ID(); ?>" title="Nyhet - <?php the_title_attribute(); ?>">
			<?php the_title('<p class="news-titel">', '</p>'); ?>
			<div class="news-excerpt"><?php the_excerpt(); ?></div>
			<p class="news-date"><?php the_time('F j, Y'); ?></p>
			</a>
			</div> <!-- end newsdescripton -->
			<div class="news-tag"></div>
		</div> <!-- end newsbox -->
		<?php endif;
		endwhile;
	endif;
	// reset the query since we used the_post()
	wp_reset_query();
	?>
	<!-- stop looping in thumbnails -->
	</div> <!-- end thumbnails -->