related_posts

<?php

function related_posts ($post_id, $post_type = 'post', $taxonomy = 'tag', $max_posts = false)
{
	$terms = get_the_terms($post_id , $taxonomy);
	$term_ids = array();
	$result = array();

	# If max_posts isn't provided, fall back to global posts_per_page option
	if (!$max_posts)
	{
		$max_posts = get_option('posts_per_page');
	}
	
	# Map array of term ojects to an array of term ID's
	if (!empty($terms)) foreach ($terms as $term)
	{
		array_push($term_ids, $term->term_id);
	}

	if (!empty($term_ids))
	{
		$related_posts = new WP_Query(array(
			'post_type' => $post_type,
			'posts_per_page' => $max_posts,
			'post__not_in' => array($post_id),
			'tax_query' => array(array(
				'taxonomy' => $taxonomy,
				'field' => 'id',
				'terms' => $term_ids
			))
		));

		if ($related_posts->have_posts())
		{
			foreach ($related_posts->posts as $related_post)
			{
				array_push($result, $related_post);
			}
		}
	}

	return $result;
}