Query parameters in Wordpress

Introduction

Query parameters let you filter or change what content WordPress shows by adding extra information to the URL.

You want to show posts from a specific category on a page.

You want to display search results based on user input.

You want to list posts by a certain author.

You want to paginate posts to show a limited number per page.

You want to filter posts by custom fields or tags.

Syntax

Wordpress

query_posts( array( 'key' => 'value', 'key2' => 'value2' ) );

Use an associative array to set query parameters.

Common keys include 'category_name', 'author', 'posts_per_page', 'paged', and 's' for search.

Examples

This shows posts only from the 'news' category.

Wordpress

query_posts( array( 'category_name' => 'news' ) );

This shows posts written by the author with ID 3.

Wordpress

query_posts( array( 'author' => 3 ) );

This shows 5 posts per page and displays the second page of results.

Wordpress

query_posts( array( 'posts_per_page' => 5, 'paged' => 2 ) );

This shows posts that match the search term 'apple'.

Wordpress

query_posts( array( 's' => 'apple' ) );

Sample Program

This WordPress template shows the 3 latest posts from the 'news' category. It uses query_posts with query parameters to filter posts. It loops through the posts and displays their titles and excerpts.

Wordpress

<?php
/* Template Name: Custom Query Example */
get_header();

// Show 3 latest posts from category 'news'
query_posts(array('category_name' => 'news', 'posts_per_page' => 3));

if (have_posts()) :
  while (have_posts()) : the_post();
    ?>
    <h2><?php the_title(); ?></h2>
    <p><?php the_excerpt(); ?></p>
    <?php
  endwhile;
else :
  echo '<p>No posts found.</p>';
endif;

wp_reset_query();
get_footer();
?>

Important Notes

Always use wp_reset_query() after query_posts() to avoid conflicts.

For better performance and flexibility, consider using WP_Query instead of query_posts.

Query parameters can be combined to create complex filters.

Summary

Query parameters filter WordPress content by adding conditions to the query.

They are passed as an array to query_posts or WP_Query.

Use them to show posts by category, author, search term, or pagination.

Practice

1. What is the main purpose of query parameters in WordPress when used with WP_Query?

easy

A. To create new user accounts automatically

B. To change the WordPress theme dynamically

C. To add custom CSS styles to posts

D. To filter and retrieve specific posts based on conditions like category or author

Solution

1. Step 1: Understand the role of query parameters

   Query parameters are used to specify conditions for retrieving posts, such as filtering by category or author.

2. Step 2: Identify the correct purpose in WordPress context

   They do not change themes, add styles, or create users; they filter content queries.

3. Final Answer:

   To filter and retrieve specific posts based on conditions like category or author -> Option D

4. Quick Check:

   Query parameters filter posts = D [OK]

Hint: Query parameters filter posts by conditions like category or author [OK]

Common Mistakes:

• Thinking query parameters change themes
• Confusing query parameters with styling or user management
• Assuming query parameters create new content

2. Which of the following is the correct way to query posts from category with ID 5 using WP_Query?

easy

A. $query = new WP_Query(array('category' => 5));

B. $query = new WP_Query(array('cat' => 5));

C. $query = new WP_Query(array('category_name' => 5));

D. $query = new WP_Query(array('category_id' => 5));

Solution

1. Step 1: Recall correct parameter for category ID

   The correct parameter to filter by category ID is 'cat', not 'category', 'category_name', or 'category_id'.

2. Step 2: Verify syntax correctness

   $query = new WP_Query(array('cat' => 5)); uses 'cat' with the ID 5 correctly in an array for WP_Query.

3. Final Answer:

   $query = new WP_Query(array('cat' => 5)); -> Option B

4. Quick Check:

   Category ID filter uses 'cat' = C [OK]

Hint: Use 'cat' key for category ID in WP_Query parameters [OK]

Common Mistakes:

• Using 'category' instead of 'cat' for category ID
• Passing category ID as 'category_name'
• Using 'category_id' which is invalid

3. What will be the result of this code snippet?

$args = array('author' => 3, 'posts_per_page' => 2);
$query = new WP_Query($args);
while ($query->have_posts()) {
  $query->the_post();
  echo get_the_title() . ', ';
}

medium

A. It will display the titles of the latest 2 posts by author with ID 3

B. It will display all posts by author with ID 3

C. It will cause a syntax error because 'author' is invalid

D. It will display 2 posts from any author

Solution

1. Step 1: Analyze query parameters

   'author' => 3 filters posts by author ID 3, 'posts_per_page' => 2 limits results to 2 posts.

2. Step 2: Understand loop output

   The loop outputs the titles of these posts separated by commas.

3. Final Answer:

   It will display the titles of the latest 2 posts by author with ID 3 -> Option A

4. Quick Check:

   Author filter + limit 2 posts = B [OK]

Hint: Author ID filters posts; posts_per_page limits number shown [OK]

Common Mistakes:

• Assuming 'author' is invalid parameter
• Thinking it shows all posts by author ignoring limit
• Believing it shows posts from any author

4. Identify the error in this query parameter usage:

$args = array('category' => 'news', 'posts_per_page' => 5);
$query = new WP_Query($args);

medium

A. 'category' should be 'category_name' to filter by category slug

B. 'posts_per_page' must be a string, not a number

C. 'category' should be 'cat' with category slug

D. No error, this code works correctly

Solution

1. Step 1: Check parameter for category slug

   To filter by category slug (like 'news'), the correct parameter is 'category_name', not 'category'.

2. Step 2: Validate other parameters

   'posts_per_page' accepts a number, so that part is correct.

3. Final Answer:

   'category' should be 'category_name' to filter by category slug -> Option A

4. Quick Check:

   Category slug filter uses 'category_name' = A [OK]

Hint: Use 'category_name' for slug, 'cat' for ID in queries [OK]

Common Mistakes:

• Using 'category' instead of 'category_name' for slug
• Thinking 'posts_per_page' must be string
• Confusing 'cat' with slug instead of ID

5. You want to display posts that belong to category ID 4 or category ID 7 using WP_Query. Which query parameter array will correctly achieve this?

hard

A. array('category_name' => '4,7')

B. array('cat' => '4,7')

C. array('category__in' => array(4, 7))

D. array('cat' => array(4, 7))

Solution

1. Step 1: Understand how to query multiple categories

   To query posts in multiple categories by ID, use 'category__in' with an array of IDs.

2. Step 2: Evaluate each option

   array('cat' => '4,7') uses a string with comma which is invalid for 'cat'. array('category_name' => '4,7') uses 'category_name' with numbers which expects slugs. array('cat' => array(4, 7)) uses 'cat' with an array which is invalid.

3. Final Answer:

   array('category__in' => array(4, 7)) -> Option C

4. Quick Check:

   Multiple category IDs use 'category__in' with array = A [OK]

Hint: Use 'category__in' with array for multiple category IDs [OK]

Common Mistakes:

• Passing multiple IDs as comma string to 'cat'
• Using 'category_name' with numeric IDs
• Passing array to 'cat' which expects single ID