WordPress Custom Fields: Listing A Series Of Posts

Published by Justin Tadlock on November 01, 2007 | 50 Responses

Set up your posts:

The first thing you will need is at least two posts. You need to create a Key named “Series Name” and assign it to each post. You also need to come up with an actual name for this series, then put that in the Value box. The Key and Value need to be the same for each post. Otherwise, this won’t work.

Modify the code:

Now, open “single.php” from your theme directory. Scroll to the bottom and find the closing </div> that ends the post. This will be different with individual themes. You can place this wherever you like. My code is after the post and before the comments template.

Insert this code:

<?php // Checks to see if the post is in a series

// Get Series Name
$series_name = get_post_meta($post->ID, 'Series Name', $single = true);

// If post is in a series
if($series_name !== '') {
	// Echo the list header
	echo '<h3>Other articles in the ' . $series_name . ' series:</h3>';

Basically, this checks to see if your article is in a series at all. If it is, a header for your list is displayed. If it’s not, then the rest of the code won’t run.

Now, we need to query the database for posts specifically with the same series name as this post. We do this by narrowing the query down to the post meta Key and post meta Value.

	// Query the database for the posts
	$query_string = "
	SELECT *
	FROM $wpdb->posts
	LEFT JOIN $wpdb->postmeta ON ($wpdb->posts.ID = $wpdb->postmeta.post_id)
	WHERE $wpdb->postmeta.meta_key = 'Series Name'
	AND $wpdb->postmeta.meta_value = '$series_name'
	AND $wpdb->posts.post_status = 'publish'
	AND $wpdb->posts.post_type = 'post'
	ORDER BY $wpdb->posts.post_date ASC
	";

All that’s left to do now is output the posts in a nice, neat list. I’m currently using an unordered list (<ul>), but you can easily change this to an ordered list (<ol>). Add this last bit of code and you’re done.

	// List the posts
	$series_posts = $wpdb->get_results($query_string, OBJECT);
		if ($series_posts):
		echo '<ul>';
		foreach ($series_posts as $post):
			echo '<li>'; ?>
			<a href="<?php echo the_permalink(); ?>" title="<?php echo the_title(); ?>">
			<?php echo the_title();
			echo '</a></li>';
		endforeach;
		echo '</ul>';
		endif;
		rewind_posts();
	} // End check for series
?>

This is a little more complicated than some of our other scripts in the Wordpress custom field series because of the database query. If you noticed, I changed a little something with the naming of the Key in this post of the series. Do you know what it is?

I capitalized the name and used a space between the words: “Series Name.” In the previous posts, this would have looked like “series-name.” The reason I changed, was to show you a different way to name your Keys. You should note that custom field Keys are case-sensitive.

What if I use a related entries plugin?

I use a related posts plugin on this site, and this is quite useless when I’m customizing my related posts with this method. I’m going to fix this little problem by using a PHP “else” statement.

So, if this post is in a series, my related posts are replaced by my list of the posts in the series. The related posts plugin is used if the post is not in a series.

<?php
else {
	if(function_exists('related_posts')) { ?>
		<h3>Related Posts</h3>
		<ul>
			<?php related_posts(); ?>
		</ul>
		<?php }
	} // end else ?>

Custom post titles in the list:

If you want to add custom titles to individual articles specifically for this list, you can create a Key named “Series Article” and give it a Value of “Your Custom Title.” This might be useful if your titles are something like “Example Series: Bla Bla Bla” and “Example Series: Yada Yada Yada.” You may want to remove the “Example Series” part because your readers will already know what series of articles this is.

In the above code, replace the code between the “foreach” and “endforeach” with this:

// get article titles
$series_article = get_post_meta($post->ID, 'Series Article', $single = true);
echo '<li>'; ?>
<a href="<?php echo the_permalink(); ?>" title="<?php echo the_title(); ?>">
<?php if($series_article !== '') echo $series_article; else echo the_title();
echo '</a></li>';

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Posted in WordPress Tagged Custom Fields, WordPress

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