Practice

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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

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.
Step 2: Identify the correct purpose in WordPress context
They do not change themes, add styles, or create users; they filter content queries.
Final Answer:
To filter and retrieve specific posts based on conditions like category or author -> Option D
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

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

Step 1: Analyze query parameters
'author' => 3 filters posts by author ID 3, 'posts_per_page' => 2 limits results to 2 posts.
Step 2: Understand loop output
The loop outputs the titles of these posts separated by commas.
Final Answer:
It will display the titles of the latest 2 posts by author with ID 3 -> Option A
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

Step 1: Check parameter for category slug
To filter by category slug (like 'news'), the correct parameter is 'category_name', not 'category'.
Step 2: Validate other parameters
'posts_per_page' accepts a number, so that part is correct.
Final Answer:
'category' should be 'category_name' to filter by category slug -> Option A
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

Step 1: Understand how to query multiple categories
To query posts in multiple categories by ID, use 'category__in' with an array of IDs.
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.
Final Answer:
array('category__in' => array(4, 7)) -> Option C
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

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
URLs with many unique query parameters	No direct impact	No direct impact	No direct impact	[X] Bad
Clean URLs or path parameters without query strings	No direct impact	No direct impact	No direct impact	[OK] Good

Query parameters in Wordpress - Performance & Optimization

Practice

Solution

Step 1: Understand the role of query parameters

Step 2: Identify the correct purpose in WordPress context

Final Answer:

Quick Check:

Solution

Step 1: Recall correct parameter for category ID

Step 2: Verify syntax correctness

Final Answer:

Quick Check:

Solution

Step 1: Analyze query parameters

Step 2: Understand loop output

Final Answer:

Quick Check:

Solution

Step 1: Check parameter for category slug

Step 2: Validate other parameters

Final Answer:

Quick Check:

Solution

Step 1: Understand how to query multiple categories

Step 2: Evaluate each option

Final Answer:

Quick Check:

Ready to prove it?