WordPress 3 comes with the ability to create Custom Post Types, which makes it very simple for us developers to extend WordPress and use it as a proper CMS for any business need. Apart from the default Posts and Pages, we can now create custom types to better suit our content, and make it easier for users to update the site.

First up, to clear some misconceptions, Custom Post Types should be thought of more as Custom Content Types, as this avoids the confusion with WordPress inbuilt Posts. So with the advent of Custom Post Types we now have the following possibilities:

1. Posts 
   WP default content type, normally used for blog posts. Posts are normally displayed in the blog in reverse sequential order by time (newest posts first). Posts are also used for creating the feeds.
2. Pages 
   WP default content type, normally used for static pages. They are similar to posts but live outside the normal time based structure of posts. They can also use special Page Templates to display them. Pages can also be organized in a hierarchical structure, with Pages being parents to other Pages.
3. Custom Post Types
   Can be anything we want them to be as we create and customise them ourselves. Think of them as Custom Content Types.

To be 100% accurate I must also mention that Attachments, Revisions and Nav Menus are also default WordPress post types.

Internally, post types are all stored in the same place, in the wp_posts table. These are differentiated by a field called post_type.

Custom Post Types can be created manually or through a plugin. I tend to prefer the manual way as it gives you the most flexibility and is the only way to properly learn how custom post types are constructed. If you have no experience in coding however, there are some plugins which make it much easier for you to create custom post types.

Let’s take a look at how to create Custom Post Types using a plugin first, then do the same in a manual way.

Creating Custom Post Types, Metaboxes and Custom Fields via Plugins

I did mention above that I prefer the manual way to creating custom post types. However on many a project recently I’ve been leaning on a new gem of a plugin. Actually, it’s not one plugin but two plugins that go hand in hand and are by far the most powerful plugins for custom post types and fields. I’m talking about Types and Views.

Introduction to Types

Types includes everything a web developer needs to customize the WordPress admin. The base Types plugin includes:

• Custom post types management
• Custom fields management
• Post relationship management

You can get additional functionality using Types add-on plugin:

• Types Access – comprehensive roles access management for different content types

[youtube]http://www.youtube.com/watch?v=unUbOoRaQmE[/youtube]

Introduction to Views

Views is an amazing plugin that aids you in displaying custom fields in your theme. It not only helps you display the fields but also do more advanced operations with them, and is unique in its area.

[youtube]http://www.youtube.com/watch?v=WQOlHu9nVkQ[/youtube]

Definitely check this hot pair of plugins out!

Download Views | Download Types

Another great plugin I’ve found for custom fields is the aptly titled Advanced Custom Fields. You can also buy add-ons through the developer’s site, but the main plugin is free. Definitely one to check out if you’re looking for a way to really do some advanced customisations through custom fields, such as adding layout fields, repeating fields, etc.

If you’re looking for a plugin with which you can not only create custom post types, custom fields, and custom taxonomies, but also export them for use in themes (without a plugin), then your answer is Easy Custom Content Types by Pippin Williamson.

Creating a Custom Post Type Manually

In order to learn how to create custom post types manually, we can use another example. This time I will be creating a somewhat simpler custom type called ‘Websites’. This post will be used for displaying interesting websites which I recommend. It could easily be used as a portfolio if you are a web designer, for example.

In our example, I want to have the following fields in my Websites content type:

• Title
• Description
• URL
• Screenshot

I will be using the WP default title and editor for the first two fields, then add a custom meta box for the other two.

First up, I need to define the new custom post type in functions.php:

[php]
/* Add Websites Custom Post Type */
add_action( ‘init’, ‘create_website_type’ );

function create_website_type() {
register_post_type( ‘website’,
array(
‘labels’ => array(
‘name’ => __( ‘Websites’ ),
‘singular_name’ => __( ‘Website’ ),
‘add_new’ => __( ‘Add New Website’ ),
‘add_new_item’ => __( ‘Add New Website’ ),
‘edit’ => __( ‘Edit Website’ ),
‘edit_item’ => __( ‘Edit Website’ ),
‘new_item’ => __( ‘Add New Website’ ),
‘view’ => __( ‘View Website’ ),
‘view_item’ => __( ‘View Website’ ),
‘search_items’ => __( ‘Search Websites’ ),
‘not_found’ => __( ‘No Websites Found’ ),
‘not_found_in_trash’ => __( ‘No Websites found in Trash’ ),
),
‘description’ => __(‘Websites to be shown in Resources section.’),
‘public’ => true,
‘show_ui’ => true,
‘publicly_queryable’ => true,
‘exclude_from_search’ => false,
‘menu_position’ => 20,
‘supports’ => array( ‘nothing’ ),
‘can_export’ => true
)
);
}
[/php]

I won’t be going through the parameters but you could read about them in the WordPress Codex Function Reference: register_post_type.

Note that the above code creates a custom post type with page-like functionality. If you would like the custom post type to behave more like a post, with no hierarchical options but the ability to associate to tags and categories, you can add the following parameters just below the ‘can_export’ parameter:

[php]
‘hierarchichal’ => false,
‘capability_type’ => ‘post’,
[/php]

Creating Custom Meta Boxes

Once we have registered our new post type we should be able to see it in the WordPress admin. It is now time to add the custom meta box. I am going to call it ‘Website Details’ and it will contain the fields ‘url’ and ‘screenshot’:

[php]
/* Add Custom Meta Box to Websites Post Type */

$new_meta_boxes =
array(
‘url’ => array(
‘name’ => ‘url’,
‘std’ => ”,
‘title’ => ‘URL’,
‘description’ => ‘Enter the site’s URL here.’),
‘screenshot’ => array(
‘name’ => ‘screenshot’,
‘std’ => ”,
‘title’ => ‘Screenshot’,
‘description’ => ‘Enter a link to the screenshot of the site.’)
);

function new_meta_boxes() {
global $post, $new_meta_boxes;
foreach ($new_meta_boxes as $meta_box) {
$meta_box_value = get_post_meta($post->ID, $meta_box[‘name’], true);
if($meta_box_value == ”)
$meta_box_value = $meta_box[‘std’];
echo’<input id=”.$meta_box[‘name’].’_noncename’ type=’hidden’ name=”.$meta_box[‘name’].’_noncename’ value=”.wp_create_nonce( plugin_basename(__FILE__) ).” />’;
echo’
<strong>’.$meta_box[‘title’].’</strong>’;
echo’<input style=’width: 100%; margin-top: 5px;’ type=’text’ name=”.$meta_box[‘name’].” value=”.$meta_box_value.” />

‘;
echo’
<em><label for=”.$meta_box[‘name’].”>’.$meta_box[‘description’].’</label></em>

‘;
}
}

function create_meta_box() {
if ( function_exists(‘add_meta_box’) ) {
add_meta_box( ‘new-meta-boxes’, ‘Website Details’, ‘new_meta_boxes’, ‘website’, ‘normal’, ‘high’ );
}
}

function save_postdata( $post_id ) {
global $post, $new_meta_boxes;

foreach($new_meta_boxes as $meta_box) {
// Verify
if ( !wp_verify_nonce( $_POST[$meta_box[‘name’].’_noncename’], plugin_basename(__FILE__) )) {
return $post_id;
}

if ( ‘page’ == $_POST[‘post_type’] ) {
if ( !current_user_can( ‘edit_page’, $post_id ))
return $post_id;
} else {
if ( !current_user_can( ‘edit_post’, $post_id ))
return $post_id;
}

$data = $_POST[$meta_box[‘name’]];

if(get_post_meta($post_id, $meta_box[‘name’]) == ”)
add_post_meta($post_id, $meta_box[‘name’], $data, true);
elseif($data != get_post_meta($post_id, $meta_box[‘name’], true))
update_post_meta($post_id, $meta_box[‘name’], $data);
elseif($data == ”)
delete_post_meta($post_id, $meta_box[‘name’], get_post_meta($post_id, $meta_box[‘name’], true));
}
}

add_action(‘admin_menu’, ‘create_meta_box’);
add_action(‘save_post’, ‘save_postdata’);
[/php]

You might have noticed in the code above, that we are using Nonces for security purposes. If you don’t know what that is, I suggest you check out this excellent post about WP nonces on Mark Jaquith’s blog.

A good place to learn about adding new meta boxes is the WordPress Codex, specifically the function reference for add_meta_box.

Another excellent tutorial for creating meta boxes, also including file and image upload can be found in this article on DeluxeBlogTips.

An excellent class that simplifies the creation of metaboxes is WPAlchemy Metabox.

Another plugin which facilitates creation of metaboxes, without a UI (aimed towards developers: Custom-Metadata

Choosing Columns to Display in Post List

Next you can also edit the columns displayed in your list view:

[php]
/* Customise columns shown in list of custom post type */
add_action(‘manage_posts_custom_column’, ‘my_custom_columns’);
add_filter(‘manage_edit-website_columns’, ‘my_website_columns’);

function my_website_columns($columns)
{
$columns = array(
‘cb’ => ‘<input type=’"checkbox"’ />’,
‘title’ => ‘Website’,
‘url’ => ‘URL’,
);
return $columns;
}

function my_custom_columns($column)
{
global $post;
if (‘ID’ == $column) echo $post->ID;
elseif (‘url’ == $column) {
$url = get_post_meta($post->ID, ‘url’, $single=true);
echo ‘<a href=’$url’>$url</a>’;
}
}
[/php]

Note: If you delete the code for creating custom post types from your functions.php, or uninstall a custom post types plugin, the custom posts you had created will still remain in the database.

Displaying Custom Post Types

To display custom post types in your front end, you could make a loop as follows:

[php]
<?php $loop = new WP_Query( array( ‘post_type’ => ‘website’, ‘posts_per_page’ => 0 ) );

while ( $loop->have_posts() ) : $loop->the_post(); ?>

<?php the_title( ‘<br ?>
<h2><a title=” . the_title_attribute( ‘echo=0′ ) . ” href=” . get_permalink() . ” rel=’bookmark’>’, ‘</a></h2>

‘ ); ?>
<div><?php the_content(); ?>
<?php if(get_post_meta($post->ID, ‘screenshot’, $single = true) != ”) :
?>
<img src=’"<?php’ alt=” />ID, ‘screenshot’, $single = true); ?>’ alt=’<?php the_title(); ?>’ />
<?php endif; if(get_post_meta($post->ID, ‘url’, $single = true) != ”) :
echo get_post_meta($post->ID, ‘url’, $single = true);
endif;

?></div>

<?php endwhile; ?>

[/php]

Listing Pages of a Custom Post Type

[php]<?php wp_list_pages( array( ‘post_type’, ‘something’ ) ); ?>[/php]

Themes, Plugins and Websites Which Implement Custom Post Types

A number of themes and plugins implement the Custom Post Types functionality and are an excellent source of reference when learning about this functionality. Here are a few of them:

• Quality Control
  A free innovative theme using custom post types to manage bug reports.
• The Events Calendar
  Uses custom post types to create events. Allows you to set a start and end time, location and address.
• Estate
  A real estate theme by Woo Themes that uses custom post types for property listings.
• WP Bids
  Uses a custom post type to generate client proposals and job estimates.
• TBTestimonials
  Manage your client testimonials with Custom Post Types. There’s even a spiffy widget.
• Rotary
  A free theme with a slider for custom post type images.
• CPT Speakers
  This plugin creates a custom post type for event speakers. Includes speakers page and single-speakers page templates.

WPMayor also has two sections powered by Custom Post Types. The ‘Books’ section was created using the More Types plugin while the ‘Websites’ section was created manually using code in the theme’s functions.php file.

Other Custom Post Type Plugins

Post Type Switcher

What happens when you already have posts and want to switch them over to your new custom post type? Or just want to change a Post into a Page, for example? Enter Post Type Switcher, a really cool plugin that makes you do that with no fuss. After installing it, the plugin will add a ‘Post Type’ interface on your ‘Edit Post’ screen, just above the ‘Publish’ button. You can use this interface to change post types as required.

Changing Custom Post Type Order

If you would like to change the order of custom post types the Custom Post Type Order plugin lets you do just that, and features a drag and drop interface that is really easy and ituitive to use.

Posts to Posts for Many to Many Relationships

The Posts to Posts plugin allows you to create many-to-many relationships between posts of all types. The relationships are stored in a hidden taxonomy. Check out the documentation explaining its usage.

Manually Selecting Related Posts

The Custom Post Type Relationships plugin allows you to set relationships between your posts (as an alternative to automated tools such as YARPP). Most of the “related posts” plugins out there while they provide some kind of control on how to create related posts, they all rely on an algorithm and the results are automatic. Custom Posts Types Relationships is a WordPress plugin that allows you to define relationships between posts in a manual way. This second version of the plugin now supports posts, pages and custom posts types, as well as allow you to define cross-type relationships. Sure, plugins that automatically get the job done are nice, but cat take you that far as they might link to irrelevant posts or change the output as more posts are added.

Custom Post Type Archives

The Custom Post Type Archives plugin will enable custom post type archives (also yearly, monthly and daily) together with feeds, customizable titles and paging. These archives will work the same way as the category or tag archives work when you go to, for example, http://example.com/category/example.

Custom Post Type Permalinks

The Custom Post Permalinks plugin will set up custom post type permalinks for non-hierarchical permalinks which have the flexibility of blog post permalinks. So, for example, I could have a press release post type and set up permalinks like so:

• http://my-site.com/press-releases/2010/08/great-news/

which would also enable post type specific archives:

• http://my-site.com/press-releases/2010/08/
• http://my-site.com/press-releases/2010/

Alternatives to Custom Post Types

If for some reason you are not happy with Custom Post Types I recommend checking out Pods, which delivers the same basic functionality as Custom Post Types, but is an altogether different beast with some important differences in the way it implements custom content types. Going into it is out of the scope of this post, but do check out the website of this ambitious CMS framework project especially if you are doing some advanced content management and need a very flexible system.

Other Useful Resources

WordPress Codex – Custom Post Types

Custom Post Type Code Generator