Wordpress: Previous/Next buttons on custom data types in meaningful order?-CodePudding

I have a website with 100 posts of a custom post type. On the single pages of each post, I would like to have a “Previous” and “Next” link to quickly jump to, you guessed it, the previous or next post.

I thought that was going to be easy, and I made these links:

<?php $prev_post = get_previous_post();
  if ($prev_post) {
   echo '<a rel="prev" href="' . get_permalink($prev_post->ID) . '">Previous</a>';
  } ?>
            
<?php $next_post = get_next_post();
  if ($next_post) {
   echo '<a rel="next" href="' . get_permalink($next_post->ID) . '">Next</a>';
  } ?>

Except those does not work. Instead of a hundred posts I can navigate through, it only allows me to jump through 5 posts. And random ones too: it goes from #1 to #15, then #40, #58, #80. Or if I decide to start from #100 and click previous, it goes to #79, then #40, #39 and #1.

It’s all very random. I have no clue what order this is and why it does not have all the posts.

Ideally I would like to go through the posts in alphabetical order of their slug. Ignoring taxonomy.

Anyone know how to do this? Thanks!

CodePudding user response：

Try this , but replace the post type.

if( get_adjacent_post(false, '', false) ) { 
    next_post_link('%link', '&larr; Previous project');
} else { 
    $last = new WP_Query('post_type=project&posts_per_page=1&order=DESC'); $last->the_post();
    echo '<a href="' . get_permalink() . '">&larr; Previous project</a>';
    wp_reset_query();
}; 


if( get_adjacent_post(false, '', true) ) { 
    previous_post_link('%link', 'Next project &rarr;');
} else { 
    $first = new WP_Query('post_type=project&posts_per_page=1&order=ASC'); $first->the_post();
    echo '<a href="' . get_permalink() . '">Next project &rarr;</a>';
    wp_reset_query();
};

CodePudding user response：

Looking more into it, I managed to solve it like that:

<?php
$criteria = array( 
    'post_type' => 'data_type',
    'orderby' => 'slug',
    'order' => 'ASC',
    'posts_per_page' => -1
);  
$posts = get_posts($criteria);
$ids = array();
foreach ($posts as $thepost) {
    $ids[] = $thepost->ID;
}
$index = array_search($post->ID, $ids);
$previd = $ids[$index - 1];
$nextid = $ids[$index   1];
if ($previd) { ?>
    <a rel="prev" href="<?php echo get_permalink($previd) ?>">Previous</a>
<?php }
if ($nextid) { ?>
    <a rel="next" href="<?php echo get_permalink($nextid) ?>">Next</a>
<?php } ?>

The limit of 5 posts was fixed with 'posts_per_page' => -1. The rest seems too complex for what is actually needed. If anyone knows of a simpler way closer to get_previous_post() I initially tried, I’m still interested.