# Oldest Posts First in Selected Categories

> Lists posts in the categories you choose from oldest to newest, so serialized stories, courses and step-by-step series read in the right order.

- Type: PHP
- Runs: Run everywhere
- Category: [Archives](https://wpide.com/library/category/archive/)
- Tags: archives, categories, ordering
- Author: WPIDE Team
- Installs: 0
- Updated: 2026-10-28
- Page: https://wpide.com/library/oldest-first-in-selected-categories/

## Code

```php
// Category slugs whose archives list posts oldest first, for series, stories and step-by-step courses. Empty = off.
// Example: array( 'my-novel', 'beginner-course' )
$wpide_oldest_first_categories = array();

add_action( 'pre_get_posts', function ( $query ) use ( $wpide_oldest_first_categories ) {
    if ( ! $wpide_oldest_first_categories || is_admin() || ! $query->is_main_query() || ! $query->is_category( $wpide_oldest_first_categories ) ) {
        return;
    }

    $query->set( 'orderby', 'date' );
    $query->set( 'order', 'ASC' );
    $query->set( 'ignore_sticky_posts', true );
} );
```

## Notes

The category list is empty by default; add the slugs of your series categories.

## How to use it

Install the free WPIDE plugin (https://wordpress.org/plugins/wpide/), find "Oldest Posts First in Selected Categories" in its snippet library and add it in one click; or create a new PHP snippet in WPIDE (or any code snippets plugin) and paste the code above. More snippets: https://wpide.com/library/