Custom post type queries in Wordpress - Mini Project: Build & Apply

Custom Post Type Queries in WordPress

📖 Scenario: You are building a WordPress site for a local library. The library wants to display a list of books separately from regular blog posts. Each book is stored as a custom post type called book.Your task is to create a simple query to fetch and display these books on a page.

🎯 Goal: Build a WordPress template snippet that queries the book custom post type and displays the title of each book.

📋 What You'll Learn

Create a query to get posts of the custom post type book

Set the number of posts to fetch to 5

Loop through the query results and display each book's title

Reset the post data after the loop

💡 Why This Matters

🌍 Real World

Libraries, bookstores, or any site that needs to show custom content types separately from blog posts can use this technique.

💼 Career

Understanding custom post type queries is essential for WordPress developers building custom themes and plugins.

1

Create the initial query arguments

Create an array called $args with these exact entries: 'post_type' => 'book' and 'posts_per_page' => 5.

Wordpress

# Your code here

Hint

Use an associative array with keys 'post_type' and 'posts_per_page'.

2

Create the WP_Query object

Create a variable called $book_query and assign it a new WP_Query object using the $args array.

Wordpress

$args = array(
    'post_type' => 'book',
    'posts_per_page' => 5
);
# Your code here

Hint

Use new WP_Query($args) to create the query object.

3

Loop through the query results and display titles

Write a while loop that runs while $book_query->have_posts() is true. Inside the loop, call $book_query->the_post() and then output the book title using the_title().

Wordpress

$args = array(
    'post_type' => 'book',
    'posts_per_page' => 5
);

$book_query = new WP_Query($args);
# Your code here

Hint

Use while ($book_query->have_posts()) and inside call $book_query->the_post() before the_title().

4

Reset post data after the loop

After the loop, call wp_reset_postdata() to restore the original post data.

Wordpress

$args = array(
    'post_type' => 'book',
    'posts_per_page' => 5
);

$book_query = new WP_Query($args);

while ($book_query->have_posts()) {
    $book_query->the_post();
    the_title('', '');
}
# Your code here

Hint

Call wp_reset_postdata() after the loop to avoid conflicts with other queries.

Practice

1. What is the main purpose of using post_type in a WP_Query in WordPress?

easy

A. To fetch posts of a specific custom post type

B. To change the theme of the website

C. To update the WordPress core version

D. To delete all posts from the database

Solution

1. Step 1: Understand WP_Query parameters

   The post_type parameter in WP_Query specifies which type of posts to fetch, such as posts, pages, or custom types.

2. Step 2: Identify the purpose of post_type

   It filters the query to only return posts of the given type, allowing you to get custom content.

3. Final Answer:

   To fetch posts of a specific custom post type -> Option A

4. Quick Check:

   post_type filters posts by type = A [OK]

Hint: Remember: post_type selects which content type to get [OK]

Common Mistakes:

• Confusing post_type with theme or plugin settings
• Thinking post_type deletes or updates posts
• Using post_type to change site appearance

2. Which of the following is the correct way to query a custom post type named 'product' using WP_Query?

easy

A. new WP_Query(array('post_type' => 'product'));

B. new WP_Query('post_type' = 'product');

C. WP_Query('post_type' => 'product');

D. new WP_Query(array('posttype' => 'product'));

Solution

1. Step 1: Check WP_Query syntax

   The correct syntax uses new WP_Query(array('post_type' => 'product')) with an associative array and the correct key post_type.

2. Step 2: Identify errors in other options

   new WP_Query('post_type' = 'product'); uses wrong assignment syntax, C misses new keyword, and D misspells post_type.

3. Final Answer:

   new WP_Query(array('post_type' => 'product')); -> Option A

4. Quick Check:

   Correct array syntax with 'post_type' key = B [OK]

Hint: Use new WP_Query with array and 'post_type' key [OK]

Common Mistakes:

• Using '=' instead of '=>' in array
• Omitting 'new' keyword
• Misspelling 'post_type' as 'posttype'

3. Given the following code, what will be the output if there are 3 'event' posts?

 $query = new WP_Query(array('post_type' => 'event'));
 if ($query->have_posts()) {
   while ($query->have_posts()) {
     $query->the_post();
     echo get_the_title() . ', ';
   }
 }
 wp_reset_postdata();

medium

A. Syntax error due to missing semicolons

B. No output because 'event' is not a default post type

C. Only the first event post title printed

D. Titles of all 3 event posts separated by commas

Solution

1. Step 1: Understand WP_Query loop behavior

   The loop runs while have_posts() returns true, iterating over all posts of type 'event'.

2. Step 2: Output titles of all posts

   Inside the loop, get_the_title() prints each post's title followed by a comma, so all 3 titles appear separated by commas.

3. Final Answer:

   Titles of all 3 event posts separated by commas -> Option D

4. Quick Check:

   Loop prints all titles = C [OK]

Hint: Loop with have_posts() prints all matching posts [OK]

Common Mistakes:

• Assuming only default post types work
• Thinking loop prints only one post
• Confusing syntax errors with correct code

4. Identify the error in this custom post type query code:

 $args = array('post_type' => 'book');
 $query = WP_Query($args);
 if ($query->have_posts()) {
   while ($query->have_posts()) {
     $query->the_post();
     the_title();
   }
 }
 wp_reset_postdata();

medium

A. Using the_title() inside the loop is invalid

B. Incorrect post_type name 'book'

C. Missing 'new' keyword before WP_Query instantiation

D. Missing wp_reset_postdata() call

Solution

1. Step 1: Check WP_Query instantiation

   WP_Query must be instantiated with the new keyword. The code misses new before WP_Query($args).

2. Step 2: Verify other parts

   The post_type 'book' is valid if registered, wp_reset_postdata() is present, and the_title() is valid inside the loop.

3. Final Answer:

   Missing 'new' keyword before WP_Query instantiation -> Option C

4. Quick Check:

   WP_Query needs 'new' keyword = D [OK]

Hint: Always use 'new' when creating WP_Query objects [OK]

Common Mistakes:

• Forgetting 'new' keyword
• Assuming post_type names are always wrong
• Thinking wp_reset_postdata() is optional

5. You want to query a custom post type 'movie' but only show posts published in 2023. Which WP_Query argument array correctly achieves this?

hard

A. { 'post_type' => 'movie', 'year' => 2023 }

B. { 'post_type' => 'movie', 'date_query' => array(array('year' => 2023)) }

C. { 'post_type' => 'movie', 'meta_key' => 'year', 'meta_value' => 2023 }

D. { 'post_type' => 'movie', 'post_status' => '2023' }

Solution

1. Step 1: Understand filtering by date in WP_Query

   To filter posts by year, use the date_query parameter with an array specifying the year.

2. Step 2: Evaluate each option

   { 'post_type' => 'movie', 'date_query' => array(array('year' => 2023)) } correctly uses date_query with year 2023. { 'post_type' => 'movie', 'year' => 2023 } uses an invalid 'year' key. { 'post_type' => 'movie', 'meta_key' => 'year', 'meta_value' => 2023 } filters by meta fields, not post date. { 'post_type' => 'movie', 'post_status' => '2023' } misuses post_status.

3. Final Answer:

   { 'post_type' => 'movie', 'date_query' => array(array('year' => 2023)) } -> Option B

4. Quick Check:

   Use date_query for year filtering = A [OK]

Hint: Use date_query array to filter posts by year [OK]

Common Mistakes:

• Using 'year' directly instead of date_query
• Confusing meta_key with post date
• Misusing post_status for date filtering