navigation link based on custom field

Question

I'm looking for a method to order posts by a custom field so that the navigational links on a single post template would point to the next or previous post in the sequence defined by a number in a custom field. Note: The posts are all in the same category. I can define the list of posts in the category in the order defined by the custom field value but when I view the single post, with a template modified to show only the selected category, the nav links at the bottom of the page are based on chronological sequence. What I need is a way to link to the next/previous post in the same category, where the order is defined by the custom field value.

Is there anyway to override the chronological ordering of the posts?

Thanks.

Answer 1

Check out get_next_post_sort and get_previous_post_sort filters. You can modify the ORDER BY clause to whatever you want (including ). For example, if you want to sort the 'next post' to be the post with the smallest adjacent post ID:

function wp28041_get_next_post_sort($where){
    return 'ORDER BY ID ASC LIMIT 1';
}
add_filter('get_next_post_sort', 'wp28041_get_next_post_sort');

You don't have to replace the entire thing, you can also add to it. For example if you'd like to add a second ordering parameter, you can:

function wp28042_get_next_post_sort($where){
    return str_replace('LIMIT 1',  ', ID ASC LIMIT 1', $where);
}
add_filter('get_next_post_sort', 'wp28042_get_next_post_sort');