Get posts in same category not working

Question

I have a custom post type with custom category taxonomy. On the CPT single templae I want to list out other posts in same categories, but I can't get it to work.

My current code:

<?php
foreach ( Roots\Sage\Utils\get_the_category_bytax( get_the_ID(), 'project_category' ) as $cat )
  $category_ids[] = $cat->term_id;

  $projects = new WP_Query( array(
    'post_status'      => 'publish',
    'post__in'         => get_post_meta( get_the_ID(), 'carbonlimits_project_related', true ),
    'post__not_in'     => array( $current_post_id ),
    'category__and'    => $category_ids,
    'post_type'        => 'project',
    'caller_get_posts' => 1,
    'posts_per_page'   => 4
  ) );

  while ( $projects->have_posts() ): $projects->the_post() ?>

    <div id="project-<?php the_ID() ?>" <?php post_class( 'col-sm-3' ) ?>>
      <a href="<?php the_permalink() ?>">
        <?php
        $thumbnail = get_the_post_thumbnail( get_the_ID(), 'project-listing' );
        if ( $thumbnail )
          echo $thumbnail;
        else
          echo '<img src="/wp-content/themes/carbonlimits/dist/images/blank.gif" width="380" height="380">';
        ?>
        <h3><?= $projects->post->post_title ?></h3>
        <span class="view-btn">View</span>
      </a>
    </div>

  <?php endwhile;
  // var_dump( $projects->request );
  wp_reset_postdata();
?>

Is it because it's a custom post type and taxonomy?

Answer 1

This should work for a custom taxonomy.

<?php
function get_related_posts() {

    global $post;

    $taxonomy = 'your_custom_taxonomy';
    $terms = wp_get_post_terms( $post->ID, $taxonomy );

    if($terms) {
        $term_arr = '';
        foreach( $terms as $term ) {
            $term_arr .= $term->slug . ','; // create array of term slugs
        }

        $args = array(
          'showposts' => 5, // you can change this to whatever you need
          'post__not_in' => array($post->ID) // exlude current post from results
          'tax_query' => array(
            array(
              'taxonomy' => $taxonomy,
              'field' => 'slug', // using 'slug' but can be either 'term_id', 'slug' or 'name'
              'terms' => $term_arr // array of ID values, slugs or names depending what 'field' is set to
            )
          )
        );
        $related_posts = get_posts( $args );

        if($related_posts) {

          foreach ( $related_posts as $post ) : setup_postdata( $post ); 
            // output whatever you want here
            the_title(); // for example
          endforeach;

        } else {

          echo 'No Related Posts';

        }

    }

    wp_reset_postdata();
}
?>