Previous/next post links displaying wrong category than is desired

Question

I want my single.php to display posts in the same category for the previous and next posts underneath the post. The problem is that each of my posts belongs to multiple categories, and they are displayed through one of the other categories (24) versus the one I want them to display from (27). Does that even make sense?

Example Categories:

Characters (parent category) (Subcategory IDs listed below:)

• 24 (This category ID displaying instead.)
• 27 (This is the category ID that I want to display.)

Now, my question is, how do I choose the category I want to be pulled from (27) instead of the one being automatically pulled (24)? Here is my code below (that I've found and been fiddling with), with what I've tried so far.

    <?php
    if (is_single() && in_category('stories')) {
        $post_id = $post->ID;
        $cat = get_the_category(); //I've tried changing this to my category (both ID and slug)
        $current_cat_id = $cat[0]->cat_ID;  //Also tried plugging ID and slug

        $args = array(
            'category' => $current_cat_id, //Also tried plugging ID and slug
            'orderby' => 'post_date',
            'order' => 'DESC'
        );
        $posts = get_posts($args);

        $ids = array();
        foreach ($posts as $thepost) {
            $ids[] = $thepost->ID;
        }

        $thisindex = array_search($post_id, $ids);
        $previd = $ids[$thisindex - 1];
        $nextid = $ids[$thisindex + 1];

        if (!empty($nextid)) {
            ?><div class="double-grid"><a rel="next" href="<?php echo get_permalink($nextid) ?>"><div class="image-tile tile-on-archive-page" style="background-image: url('<?php echo get_the_post_thumbnail_url($nextid); ?>'"> <div class="gold-button">LAST STORY >></div></div></a></div><?php
        }
        if (!empty($previd)) {
            ?><div class="double-grid"><a rel="prev" href="<?php echo get_permalink($previd) ?>"><div class="image-tile tile-on-archive-page" style="background-image: url('<?php echo get_the_post_thumbnail_url($previd); ?>'"> <div class="gold-button">NEXT STORY >></div></div></a></div><?php
        }
    }
    ?>

Answer 1

Your code problem is you get only the first category of a post because $cat[0] is the first, not current.

Inside The Loop:

<?php
previous_post_link( // prints the formatted link
    '<span>&laquo; %link</span>',  // beautifying around
    'Prev in this cat',            // the text (%link) to be used in the span above
    true,                          // confirm that you want only this category
    '',                            // no categories to exclude
    'category'                     // taxonomy name
);

echo " | "; // just a separator between next and prev

/* The same setup here, not shown to keep the answer clean */
next_post_link();

See previous_post_link() for parameters.

If you are outside of The Loop, let me know, I'll update the answer and supply the additional code and comments.

Answer 2

Hazah! I thought I'd post it here, but I worked with someone on the development forums on Wordpress.org and they actually solved the problem for me.

You can see the solution and tweaks here: WordPress.org Forum Topic