Custom taxonomies in Wordpress - Mini Project: Build & Apply

Create and Use Custom Taxonomies in WordPress

📖 Scenario: You are building a WordPress website for a book review blog. You want to organize books not only by categories but also by genres like 'Science Fiction', 'Romance', and 'Mystery'. WordPress does not have a built-in taxonomy for genres, so you will create a custom taxonomy called 'genre'.

🎯 Goal: Build a custom taxonomy called genre for the post post type. This taxonomy will let you tag posts with genres. You will register the taxonomy with proper labels and make it hierarchical like categories.

📋 What You'll Learn

Create a custom taxonomy called genre

Attach the genre taxonomy to the post post type

Make the taxonomy hierarchical (like categories)

Add labels for the taxonomy including name, singular_name, and search_items

Register the taxonomy using the init action hook

💡 Why This Matters

🌍 Real World

Custom taxonomies help organize content beyond default categories and tags, making websites easier to navigate and manage.

💼 Career

Knowing how to create and register custom taxonomies is essential for WordPress developers building custom themes and plugins.

1

Create the labels array for the custom taxonomy

Create an array called labels with these exact entries: 'name' => 'Genres', 'singular_name' => 'Genre', and 'search_items' => 'Search Genres'.

Wordpress

# Your code here

Hint

Use array() to create the labels array with the exact keys and values.

2

Create the arguments array for registering the taxonomy

Create an array called args with these exact entries: 'hierarchical' => true, 'labels' => $labels, and 'show_ui' => true.

Wordpress

 'Genres',
    'singular_name' => 'Genre',
    'search_items' => 'Search Genres'
);

# Your code here

Hint

Use array() to create the args array with the exact keys and values.

3

Register the custom taxonomy with register_taxonomy

Call register_taxonomy with these exact arguments: 'genre' as the taxonomy name, 'post' as the post type, and $args as the arguments array.

Wordpress

 'Genres',
    'singular_name' => 'Genre',
    'search_items' => 'Search Genres'
);

$args = array(
    'hierarchical' => true,
    'labels' => $labels,
    'show_ui' => true
);

# Your code here

Hint

Use register_taxonomy with the exact parameters to register the taxonomy.

4

Hook the taxonomy registration into WordPress initialization

Wrap the register_taxonomy call inside a function called create_genre_taxonomy. Then add this function to the init action hook using add_action.

Wordpress

 'Genres',
    'singular_name' => 'Genre',
    'search_items' => 'Search Genres'
);

$args = array(
    'hierarchical' => true,
    'labels' => $labels,
    'show_ui' => true
);

# Your code here

Hint

Define a function that registers the taxonomy and hook it to init using add_action.

Practice

1. What is the main purpose of creating a custom taxonomy in WordPress?

easy

A. To increase website loading speed

B. To change the website's theme colors

C. To add new user roles

D. To organize content in a way that fits your website's needs

Solution

1. Step 1: Understand what taxonomy means in WordPress

   Taxonomies group content like categories or tags to organize posts.

2. Step 2: Identify the purpose of custom taxonomies

   Custom taxonomies let you create your own groups to better fit your content.

3. Final Answer:

   To organize content in a way that fits your website's needs -> Option D

4. Quick Check:

   Custom taxonomy = organize content [OK]

Hint: Custom taxonomies organize content, not change design or speed [OK]

Common Mistakes:

• Confusing taxonomies with themes or plugins
• Thinking taxonomies affect site speed
• Mixing taxonomies with user roles

2. Which of the following is the correct way to register a custom taxonomy called genre for posts in WordPress?

easy

A. register_taxonomy('genre', 'post', array('hierarchical' => true));

B. register_taxonomy('genre', 'posts', array('hierarchical' => true));

C. register_taxonomy('genre', array('post'), 'hierarchical' => true);

D. register_taxonomy('genre', 'post', 'hierarchical' => true);

Solution

1. Step 1: Check the function signature of register_taxonomy()

   The function requires taxonomy name, object type(s) as string or array, and an array of arguments.

2. Step 2: Verify correct parameter types and syntax

   register_taxonomy('genre', 'post', array('hierarchical' => true)); uses 'post' as string and an array for arguments correctly.

3. Final Answer:

   register_taxonomy('genre', 'post', array('hierarchical' => true)); -> Option A

4. Quick Check:

   Correct syntax uses array for args and string for post type [OK]

Hint: Use array() for args and string or array for post types [OK]

Common Mistakes:

• Using plural 'posts' instead of 'post'
• Passing arguments outside an array
• Wrong parameter order

3. Given this code snippet:

register_taxonomy('genre', 'post', array('hierarchical' => true));
$terms = get_terms(array('taxonomy' => 'genre', 'hide_empty' => false));
foreach ($terms as $term) {
  echo $term->name . ', ';
}

What will this code output if there are two terms 'Fiction' and 'Non-Fiction' assigned to posts?

medium

A. genre, Fiction, Non-Fiction

B. Fiction, Non-Fiction,

C. Array

D. Error: Undefined variable

Solution

1. Step 1: Understand get_terms() usage

   get_terms() fetches terms of the taxonomy 'genre' including empty ones due to 'hide_empty' => false.

2. Step 2: Loop through terms and print their names

   The foreach loop prints each term's name followed by a comma and space.

3. Final Answer:

   Fiction, Non-Fiction, -> Option B

4. Quick Check:

   Loop prints term names separated by commas [OK]

Hint: get_terms returns term objects; loop prints their names [OK]

Common Mistakes:

• Expecting taxonomy name instead of term names
• Confusing array output with string
• Not setting 'hide_empty' causing missing terms

4. What is wrong with this code snippet for registering a custom taxonomy?

register_taxonomy('genre', 'post', 'hierarchical' => true);

medium

A. The post type should be an array, not a string

B. The taxonomy name must be plural

C. The third argument should be an array, not a key-value pair directly

D. The function name is incorrect

Solution

1. Step 1: Check the function parameters

   register_taxonomy() expects the third argument as an array of arguments.

2. Step 2: Identify the error in argument format

   The code passes 'hierarchical' => true directly, not inside an array, causing syntax error.

3. Final Answer:

   The third argument should be an array, not a key-value pair directly -> Option C

4. Quick Check:

   Args must be in array() [OK]

Hint: Always wrap arguments in array() for register_taxonomy [OK]

Common Mistakes:

• Passing arguments without array()
• Using plural taxonomy names incorrectly
• Wrong function name like register_taxonomies

5. You want to create a custom taxonomy called location that behaves like tags (non-hierarchical) and attach it to both post and event post types. Which code snippet correctly achieves this?

hard

A. register_taxonomy('location', array('post', 'event'), array('hierarchical' => false));

B. register_taxonomy('location', 'post', array('hierarchical' => false)); register_taxonomy('location', 'event', array('hierarchical' => false));

C. register_taxonomy('location', array('post', 'event'), array('hierarchical' => true));

D. register_taxonomy('location', array('post', 'event'), array('hierarchical' => true, 'tags' => true));

Solution

1. Step 1: Understand hierarchical argument for tags

   Tags are non-hierarchical, so 'hierarchical' must be false.

2. Step 2: Attach taxonomy to multiple post types

   Pass an array of post types ['post', 'event'] as second argument.

3. Step 3: Check options for correct syntax and behavior

   register_taxonomy('location', array('post', 'event'), array('hierarchical' => false)); correctly sets 'hierarchical' => false and attaches to both post types in one call.

4. Final Answer:

   register_taxonomy('location', array('post', 'event'), array('hierarchical' => false)); -> Option A

5. Quick Check:

   Non-hierarchical + multiple post types = register_taxonomy('location', array('post', 'event'), array('hierarchical' => false)); [OK]

Hint: Use array for post types and set hierarchical false for tags [OK]

Common Mistakes:

• Setting hierarchical true for tags
• Calling register_taxonomy twice unnecessarily
• Passing post types as string instead of array