Create Custom Post Types & Taxonomies

A Step-by-Step Guide: 
Create Custom Post Types & Taxonomies In WordPress

Are you ready to take your WordPress site beyond basic posts and pages? Creating custom post types and taxonomies offers a powerful way to organize and present your content in a way that suits your unique needs. In this guide, we’ll walk you through the essentials of registering a custom post type and establishing relevant taxonomies (categories), so you can enhance your site’s structure, boost discoverability, and provide visitors with a more intuitive user experiences.

What is a custom post type in WordPress?

A Custom Post Type (CPT) in WordPress is a way to add your own content types beyond the default post types like Posts, Pages, and Media. It allows you to structure and manage specific kinds of content in your WordPress site, tailored to your needs.

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What can custom post types be used for?

Custom post types allow you to structure specialized content in WordPress. Unlike default Posts or Pages, each custom post type can be tailored with unique attributes, taxonomies, and metadata, ensuring the presentation and organization match the specific needs of your website. Here are some practical ways they can be used:

What are the features of a custom post type?

A CPT behaves similarly to posts and pages but can have unique features such as:

• Custom Labels: Titles, menu names, etc., can reflect your content type (e.g., "Books" instead of "Posts").
• Custom Fields: Additional metadata for storing extra details like price, rating, or location.
• Custom Templates: Custom archive and single-view templates (e.g., archive-portfolio.php or single-event.php).
• Taxonomies: You can create custom categories or tags specific to your post type. For example locations, genre for movies, type of work for portfolio etc

Real World Examples on How to Use Custom Post Types:

How To Create a Custom Post Type in WordPress

Step 1: Setup a custom wordpress plugin.

Make sure to follow the previous steps on how to setup wordpress development environment and how to setup a custom wordpress plugin. Then you will be ready to add these code snippets to your plugin. You can also add these code snippets to your functions.php file in your theme.

How To Register a Simple Custom Post Type

Below is one of the simplest examples of registering a custom post type in WordPress. It uses the bare minimum parameters to create a public post type.

How It Works:

register_post_type()
This function registers a custom post type in WordPress. This tells WordPress how to handle, display, and manage the new content type. They can also be made public or private and tailored to work with custom taxonomies, metaboxes, and plugins. We will covered a more advanced example next.

add_action( 'init', 'create_books_cpt' );
The init hook, which fires after WordPress has finished loading but before any headers are sent. This is where many core functions are set up, making it a common and safe place to register custom post types. We’re instructing WordPress when you reach the init phase of your loading process, please run the create_books_cpt function

Custom Post Type - All The Options & Settings Explained In Detail

How It Works:

1. LABELS ARRAY: Describes the various text strings used throughout the admin interface. You can pick and choose what labels you want to change from the default.

__(...) - These functions are just used for translations. If you don't use them it wont break anything. Just considered best practice for the WordPress interface.

_x(...) Returns a translated string with a context parameter to handle words or phrases that need different translations depending on usage.

textdomain - Change to slug of your plugin so WordPress knows where to find translation files.

2. Arguments Array: Control how the CPT behaves in both the admin area and the public website. You can pick and choose what arguments you want to change from the default.

3. Register Custom Taxonomy: Works similar to registering a custom post type. Has an array of labels and arguments that plug into a function to register it. These settings can be customized to your liking.

Common Issues When Registering a Custom Post Type:

404 page not found:

Flushing Rewrite Rules:

Flushing Rewrite Pragmatically:

Adding Metaboxs & custom fields to custom post types:

How add_meta_box() Function Works:

Unique ID: 'mr_custom_fields_metabox'register_post_type()
This is a string that uniquely identifies your metabox. You reference this ID later if you need to remove or modify the same metabox. Prefixing with “mr_” helps identify that this metabox is specific to your “Movie Reviews” functionality.

Title: __( 'Movie Review Custom Fields', 'textdomain' )
The second parameter is the title that appears at the top of the metabox in the WordPress admin.
It’s wrapped in __() which is a WordPress internationalization function for translating strings.
textdomain should match the domain of your plugin if you plan to localize/transliterate this string into other languages.

Callback: 'mr_render_custom_fields_metabox'
This tells WordPress which function to call to display the contents (HTML) of the metabox.
When a user loads or edits a “Movie Review” in the admin, WordPress will execute this callback, and any HTML output from it will appear inside the metabox. You’ll typically retrieve existing values with get_post_meta(), output fields (<input>, <textarea>, etc.), and add a nonce for security.

Screen/Post Type: 'movie_review'
Here you specify which post type gets this metabox. Since you created a custom post type named movie_review, you’re telling WordPress: “This metabox should appear on the Add/Edit screens for posts belonging to the movie_review post type.” You can also pass arrays of post types if you want a single metabox to appear for multiple post types.

Context: 'normal'
Indicates where the metabox should be displayed on the Edit screen.
normal: Displays under the content editor (the main area). “normal” is typically used for custom fields that require more space or are central to your content.
side: Displays in the sidebar (where Publish box, Featured Image box, etc., usually appear).

Priority:'default'
Common Values: high, core, default, low
Determines the priority of the metabox within the chosen context. This can affect the order in which multiple metaboxes appear in the same area. “default” is a general setting; if you find your metabox is buried or overshadowed, you could try 'high'.

Hooking Into add_meta_boxes
This tells WordPress when it’s time to add metaboxes (on the Edit Post screen load), run the function mr_add_custom_fields_metabox. The add_meta_boxes hook is part of WordPress’s core plugin API. It fires on the edit screen initialization process, ensuring your custom metabox is registered at the correct time.

How to render custom fields inside your metabox:

Below is a detailed explanation of how this function renders custom fields inside a metabox on the “Movie Review” edit screen. Each part of the code plays a key role in retrieving, displaying, and securing data for your custom post type.

Retrieving Existing Values: get_post_meta()
Retrieves the value from the post meta field for the current post. The third parameter true means it returns a single value rather than an array. Each custom field (Director, Release Year, Rating, etc.) is stored under its own unique meta key. The result is stored in a variable ($director, $release_year, etc.)

Security: wp_nonce_field()
Nonce field adds a hidden HTML input to your form with a nonce (a one-time use token). Protects against Cross-Site Request Forgery (CSRF) by verifying that legitimate users (with correct permissions) are the ones submitting updates.

'mr_custom_fields_nonce_action' A unique identifier (nonce “action”) used during verification in your save_post function.

'mr_custom_fields_nonce' The name of the hidden input field. When you save data, WordPress checks that this nonce is valid before processing.

esc_html_e()
Echoes a translated (internationalized) string, escaping it for HTML to prevent XSS attacks or markup issues.

value="<?php echo esc_attr( $director ); ?>"
Dynamically populates the input with the previously saved meta value (if any), escaping it with esc_attr().

esc_textarea( $cast )
Escapes special characters for safe insertion inside a textarea.

How to save custom fields inside custom post type:

Below is a detailed explanation of each step in the function that saves the custom fields data for your “Movie Reviews” post type. This function is hooked to the save_post_movie_review action, which fires whenever a “Movie Review” post is saved or updated.

Check for User Permissions: current_user_can( 'edit_post', $post_id )
Checks if the current logged-in user has permission to edit the specific post. If they don’t have the required capability, we return (stop the function).

if ( isset( $_POST['field_name'] ) ) { ... }

Verify that the form field was submitted before saving it to the database. Ensures we only process the data if it’s actually included in the form submission. Prevents overwriting data in unexpected situations.

sanitize_text_field( $_POST['mr_director'] )

Strips out unwanted tags, slashes, or malicious code from user input. This is essential for security, ensuring you’re only storing safe text in the database.

update_post_meta( $post_id, '_mr_director', ... )

Stores the sanitized value in the wp_postmeta table, under the key _mr_director. If a value already existed, it updates it; if not, it creates a new entry. The underscore (_mr_) convention is used to denote a private meta key, preventing it from appearing by default in some admin screens or custom fields interfaces.

How To Remove Unwanted Metaboxes From Post Edit Page:

The code snippet removes (or “unregisters”) certain metaboxes from a specified custom post type in the WordPress admin. Metaboxes are those boxes or panels you see when editing a post, such as Yoast SEO, Custom Fields, etc. By removing them, you’re essentially decluttering the edit screen, which can be useful if those boxes are not relevant for certain users or post types.

Replace 'post_type_name' with the name of the custom post type you want to remove the metabox from.

How to Find the Metabox ID?

To remove a metabox, you first need its unique ID. Here’s the quickest way to find it:

1. Open the Edit Screen: Navigate to the WordPress editor where the metabox appears.
2. Right-Click & Inspect: Right-click anywhere on the metabox and select “Inspect” (or “Inspect Element,” depending on your browser).
3. Identify the ID Attribute: In the developer tools, look for the top-level HTML <div> element that wraps the metabox. The ID attribute of this element (e.g., id="wpseo_meta") is the identifier you’ll use.

Use a High Priority

Setting the priority to 9999 in the add_action ensures that your function runs last (or almost last). Some meta boxes may be added with a high priority, and you want to be sure you remove them after they are registered.

How To Change The Edit Page Table Of a Custom Post Type:

Below is an example of how to edit the “Movie Reviews” admin list page (the table at edit.php?post_type=movie_review) so that it displays three additional columns for Director, Release Year, and Rating. These columns will pull their data from the respective custom fields (_mr_director, _mr_release_year, and _mr_rating). We will also remove the comments and reorder date to always show at the end.