Single post with an image gallery

single.php

<?php get_header(); ?>

<div class="leftside">
<?php while ( have_posts() ) : the_post(); ?>
    <h3 class="title"><?php the_title(); ?></h3>

    <h4 class="date"> ... </h4>

    <div class="description">
      <?php the_content(); ?>
    </div>

    <ul class="gallery_detail">
      <?php
    $images = get_children( array( 'post_parent' => $post->ID, 'post_type' => 'attachment', 'post_mime_type' => 'image', 'orderby' => 'menu_order', 'order' => 'ASC', 'numberposts' => 999 ) );
    if ( $images ) :
      $total_images = count( $images );
      $image = array_shift( $images );
      $image_img_tag = wp_get_attachment_image( $image->ID, 'thumbnail' );
      ?>
        <li><a class="lightbox" href="<?php the_permalink(); ?>"><?php echo $image_img_tag; ?></a></li>
        <?php endif; ?>
    </ul>

<?php endwhile; ?>
</div><!-- /.leftside -->

<?php get_sidebar(); /* .rightside stuff */ ?>
<?php get_footer(); ?>