Custom Post Types And Taxonomies For Complex Wordpress Sites

Why Custom Post Types and Taxonomies Matter for Complex Sites

The default post types and taxonomies in WordPress like posts, pages, categories, and tags are useful for basic content sites. However, as a site’s functionality and content structure becomes more complex, relying solely on defaults can become limiting in key ways:

Overcoming limitations of default post types and taxonomies: With growth comes complexity, and the basics like the post post type may no longer accommodate emerging needs for different content types and relationships.
Tailoring content structure to specific needs: Custom post types allow modeled content that matches real-world entities and requirements rather than forcing data into basic posts and pages.
Enabling custom functionality and interfaces: Hooking into custom post types and taxonomies in code creates opportunities for specialized UIs, site features, and applications.

Defining custom post types and taxonomies is critical for complex sites to overcome limitations, craft tailored content models, and power custom site functionality.

Defining Custom Post Types

At the core of custom post types is the WordPress register_post_type() function. Understanding its arguments and usage paves the way for defining custom content types with all capabilities supported.

Table of Contents

register_post_type() function overview

All native and custom post types in WordPress must be registered, specifying key details via the register_post_type() function. Required and common arguments covered below:

post_type (required) – The machine-readable name like ‘post’, ‘page’, or custom identifiers.
label (required) – The human readable singular and plural names displayed in WP Admin UI.
public (optional) – Whether the post type is publicly visible and queryable. Defaults to false.
hierarchical (optional) – Whether the custom type allows parent/child like pages. Defaults to false.
menu_position (optional) – The position in admin menu order if visible.
capability_type (optional) – Post type permission level using post capability types.
supports (optional) – Enabled editor behaviors like title, editor, comments, etc.

Key arguments like ‘public’, ‘hierarchical’, etc

Understanding key arguments when registering custom post types is critical to enable needed capabilities:

public – Controls frontend visibility. Enable for publicly accessible custom content types.
exclude_from_search – Exclude from frontend search results if needed despite public.
publicly_queryable – Allows querying via WP_Query and REST API endpoints if public.
show_ui – Add admin interfaces to WP Dashboard for content management.
has_archive – Enables a custom post type archive if public.

These common arguments control critical components of publicly exposed and internally managed custom post types.

Example register_post_type() code for a “Product” custom post type

add_action( 'init', 'register_product_post_type' );
 
function register_product_post_type() {
 
  $labels = array(
    'name' => 'Products',
    'singular_name' => 'Product'
  );
   
  $args = array(
    'label' => 'Products',
    'labels' => $labels,
    'description' => 'Product inventory content type',
    'public' => true,
    'has_archive' => true, 
    'show_ui' => true,
    'capability_type' => 'post',
    'hierarchical' => false,
    'rewrite' => array('slug' => 'products'),
    'supports' => array('title','editor','thumbnail'),
    'taxonomies' => array('product_cat')
  );
       
  register_post_type( 'product', $args );
}

This demonstrates a real-world “product” custom post type registration with the necessary arguments to enable public visibility, admin management, and a product archive.

Using Custom Taxonomies to Organize Content

Custom taxonomies in WordPress provide the facility to categorize and connect related content entities. Tied to specific post types, taxonomies power organization and querying.

Taxonomy relationship to post types

All taxonomies attach to one or more specific post types rather than standing alone. This enables customized organizational structures per post type. Some key associations include:

category – Tied to post post type only.
tag – Can be used across post types like posts and products.
product_cat – Custom taxonomy exclusive for products custom post type.

Defining these relationships via registering post types and taxonomies helps manage organization.

register_taxonomy() function basics

Taxonomies are registered using the register_taxonomy() function. This enables associating terms like categories to content types posts. Required and common arguments:

taxonomy (required) – The machine name like ‘category’ or custom.
object_type (required) – Post type name/s to tie taxonomy to.
label (required) – Plural and singular term labels for UI display.
show_admin_column (optional) – Adds posts term column on listing screens.
hierarchical (optional) – Enable hierarchy/tree structure like categories.

Registering taxonomies with essential arguments establishes the content type association and management interfaces.

Example taxonomy registration for Product Categories

add_action( 'init', 'register_product_taxonomies');
  
function register_product_taxonomies() {
 
  $labels = array( 
    'name' => 'Product Categories',
    'singular_name' => 'Category'
  );
  
  register_taxonomy( 'product_cat', array('product'), array(
    'label' => 'Product Categories', 
    'labels' => $labels,
    'show_admin_column' => true,
    'hierarchical' => true,
  ));
}

This exemplifies registering a product_cat taxonomy associated with products custom post type. Enables category management UI and hierarchy.

Advanced Usage and Functionality

Moving beyond basics with custom post types and taxonomies, advanced features and functionality empower further customization for complex sites.

Custom admin interfaces with show_in_menu

The default admin UI menus may not adequately expose new custom content types. Using the show_in_menu argument when registering post types enables several interface options:

Main admin menu item positioning.
A top-level custom admin menu item.
Submenu item under another top level item like Posts.

'show_in_menu' => true, // Top level

'show_in_menu' => 'edit.php?post_type=page', // Sub Menu

Custom admin menus improve content organization and UX.

Controlling permalink structure

Define predictable URL structures for custom public post types by hooking into the post type arguments:

'rewrite' => array(
  'slug' => 'products',
  'with_front' => false 
),

This enables product custom post type URLs like https://example.com/products/sample-product/ rather than ambiguous links.

Enable revisions for reliable content editing

While custom post types do not store revisions by default, this can be added for post editing reliability:

'supports' => array(
  'revisions'
)

This provides revision history and restore options to match default post and page content types.

Developing Front-end Displays and Templates

Realizing the potential of custom post types and taxonomies relies on custom display templates and code to expose content on the front-end.

Template hierarchy and custom template files

Custom page templates like single-product.php and taxonomy-product_cat.php establish control over displays:

Single Product Display
- single-product.php
- single.php
- singular.php
- index.php

Product Category Archive
- taxonomy-product_cat.php
- archive-product.php  
- archive.php
- index.php

Custom templates mapped to custom entities override defaults for shaping presentation.

Querying custom post types with WP_Query

The WP_Query class allows crafting queries to include/exclude custom post types, specific taxonomies, and associated terms. Examples:

// Recent products
$args = array(
  'post_type' => 'product',
  'posts_per_page' => 12 
);

// News in specific categories  
$args = array(
  'post_type' => 'news',
  'tax_query' => array(
    array(
      'taxonomy' => 'news_category',
      'field'    => 'slug',
      'terms'    => array( 'breaking', 'featured' ),
    ),
  ),
);

WP_Query used on custom entities enables precise display shaping.

Displaying associated taxonomy and custom field data

Rendering taxonomy terms and custom metadata provides enriched custom post type displays:

// Get and display terms 
$terms = get_the_terms( $post->ID, 'product_cat' );  

// Output custom field
echo get_post_meta( $post->ID, 'price', true );

Associated taxonomy and field data attachments customize appearances.

Custom Post Types in Plugins and Theme Development Workflows

Developing with custom post types and taxonomies fits nicely in both plugin and theme workflows for reusability and consistency.

Registering custom post types and taxonomies

To ensure consistency, registration should happen on the ‘init’ hook:

add_action( 'init', 'register_custom_content_entities');
  
function register_custom_content_entities(){
 
  // Register custom post types
 
  // Register taxonomies
  
}

Containing registration in a single location avoids duplication.

Plugin vs. theme implementation factors

Plugins neatly package custom post functionality for re-use across sites:

Self-contained in a plugin.
Easily share and distribute.
Enable functionality via activation.

Whereas themes bake custom posts into site appearance and function:

Tightens coupling to site theme.
Provides template files for display.
Not easily reused across themes.

Choose approach based on scope and reuse needs.

Exposing data to other applications via REST API

surfacing custom post data via REST API expands integration opportunities:

// Add custom post types to REST API
add_action( 'rest_api_init', 'add_custom_post_types_to_api' );
  
function add_custom_post_types_to_api(){
  register_post_type( 'product', array(
    'show_in_rest' => true,
  )); 
}
 
// Register REST fields
register_rest_field( 'product', 
  'custom_price', 
  array(
     'get_callback'    => 'get_custom_price',
     'schema'          => null,
) );

This opens the door for mobile apps, JavaScript frameworks, and custom integrations to leverage the enriched data.

Custom Post Types And Taxonomies For Complex WordPress Sites