Pagination on category page with custom post types

Question

Wordpress is not new for me but I am really stuck on this piece of code that I can not get to work properly.

I register a custom post type News and let the custom post type use the Wordpress categories

'taxonomies' => array('category')

So far so good. I can assign different categories to the custom post type News. But I want that people can see news from a specific category. So I want that to do that with the category.php page. The problem is that the pagination is not working. I get a page not found when I go to /page/2

I use this code on a category.php page.

// Get post ID
$post_type = get_post_type( $post->ID );

// Get category ID
$category_id = get_cat_ID(single_cat_title('', false));

// Wordpress pagination
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;

// WP_Query arguments
$args_news = array (
    'post_type'             => array( 'news' ),
    'pagination'            => true,
    'posts_per_page'        => '9',
    'orderby'               => 'date',
    'paged'                 => $paged,
    'cat'                   => $category_id,
);

// The Query
$query = new WP_Query( $args_news );

// The Loop
if ( $query->have_posts() ) {
    while ( $query->have_posts() ) {
        $query->the_post(); ?>
        <div>
            <h1><?php the_title(); ?></h1>
            <p><?php the_content(); ?></p>
        </div>
<?php }

} else { 
    // no news found
}
?>

<div class="pagination">
    <div class="previous-page"><?php previous_posts_link( 'Newer Posts' );?></div>
    <div class="next-page"><?php next_posts_link( 'Older Posts', $query->max_num_pages ); ?></div>
</div>

<?php
// Reset postdata
wp_reset_postdata();

Answer 1

Before I go to your problem, I would like to start of by asking why you are using a custom query on a category page instead of the main query. You should never change the main query for a custom query on any archive page or on your home page.

WordPress provides an action hook, pre_get_posts which you can use in conjunction with conditional tags to target and modify the main query before it is executed on specific pages. For category pages the is_category() conditional check is supplied.

You could just simply do the following in your functions.php, while keeping your default loop intact on your category page. Just a tip, pre_get_posts uses the same parameters as WP_Query

function add_news_to_category( $query ) {
    if ( ! is_admin() && $query->is_category() && $query->is_main_query() ) {

         $query->set( 'post_type', array( 'news' ) );
         $query->set( 'posts_per_page', '9' );
         $query->set( 'orderby', 'date' );

    }
}
add_action( 'pre_get_posts', 'add_news_to_category' );

OK, now to your actual problem with your code.

• Firstly, you don't need to use wp_reset_query and wp_reset_postdata together. wp_reset_query is actually used in conjunction with query_posts, which you must never use, and I mean never. Just simply use wp_reset_postdata after WP_Queryandget_posts`, and remember, never forget to do that

• Secondly, look closer at your code. You have $query = new WP_Query( $args_news );, but then you have <?php next_posts_link( 'Older Posts', $custom_query->max_num_pages ); ?>. Spot the difference? $query and $custom_query. So, <?php next_posts_link( 'Older Posts', $custom_query->max_num_pages ); ?> should be <?php next_posts_link( 'Older Posts', $query->max_num_pages ); ?>

For further reading:

• When to use a custom query and when to use the main query