Modificar código para temas relacionados

<?php
$original_post = $post;
$tags = wp_get_post_tags($post->ID);
if ($tags) {
  echo '<div>Temas Relacionados</div>';
  $first_tag = $tags[0]->term_id;
  $args=array(
    'tag__in' => array($first_tag),
    'post__not_in' => array($post->ID),
    'showposts'=>4,
    'caller_get_posts'=>1
   );
  $my_query = new WP_Query($args);
  if( $my_query->have_posts() ) {
    echo "";
    while ($my_query->have_posts()) : $my_query->the_post(); ?>
<div class='tpost'>    
<a href="<?php the_permalink() ?>">
<img width="130" height="200" src="<?php getImage('1'); ?>" alt="<?php the_title(); ?>" />
</a>
<h2><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h2>
</div>

$first_tag = $tags[0]->term_id;

'tag__in' => array($first_tag),

foreach($tags as $tag) {
		$first_tag[] = $tag->term_id;
}

'tag__in' => $first_tag,