ID; $prev_thumb = get_the_post_thumbnail($prev_post_id, $pn_post_thumb_size, array( 'class' => $pn_post_thumb_class )); ?> ID; $next_thumb = get_the_post_thumbnail($next_post_id, $pn_post_thumb_size, array( 'class' => $pn_post_thumb_class )); ?>