How do I make custom query with WordPress?

When developing with WordPress, custom queries are a key feature that allows you to retrieve posts, pages, or other custom post types based on specific requirements. WordPress includes a powerful class called WP_Query, which can be used to implement custom queries. Next, I will explain in detail how to use WP_Query for custom queries, along with a practical example.

1. Initializing the WP_Query Object

First, we need to create an instance of WP_Query and define the query conditions by passing a parameter array. This array can include various parameters such as post_type, post_status, posts_per_page, etc. The complete list of parameters can be found in the WordPress Codex.

php
$args = array(
    'post_type'      => 'post', // Post type
    'posts_per_page' => 10,     // Display 10 posts per page
    'orderby'        => 'date', // Order by date
    'order'          => 'DESC'  // Descending order
);

$query = new WP_Query($args);

2. Processing Query Results

Once the WP_Query object is initialized, we can use it to retrieve posts and display the results through a loop.

php
if ($query->have_posts()) {
    echo '<ul>';
    while ($query->have_posts()) {
        $query->the_post();
        echo '<li>' . get_the_title() . '</li>'; // Display post title
    }
    echo '</ul>';
} else {
    echo 'No posts found.';
}

3. Resetting Post Data

After completing a custom query, especially in front-end templates, it's best to use the wp_reset_postdata() function to reset the global $post object, ensuring subsequent code runs correctly.

php
wp_reset_postdata();

Example: Querying Articles in a Specific Category

Suppose we need to query the latest 10 articles in the 'news' category. We can set the parameters as follows:

php
$args = array(
    'category_name'  => 'news',
    'posts_per_page' => 10
);

$query = new WP_Query($args);

if ($query->have_posts()) {
    echo '<ul>';
    while ($query->have_posts()) {
        $query->the_post();
        echo '<li>' . get_the_title() . '</li>'; // Display post title
    }
    echo '</ul>';
} else {
    echo 'No posts found.';
}

wp_reset_postdata();

This covers the basic process and example of using WP_Query for custom queries. It can be flexibly applied to various complex content query scenarios and is a core tool in WordPress customization development.