WP Related Posts by Categories

wp-related-posts.php

<?php
// Inside the post loop
          $categories = wp_get_post_categories(get_the_ID());
          $args=array(
              'category__in' => $categories, // The categories of this post
              'post__not_in' => array(get_the_ID()), // Remove current post
              'posts_per_page'=> 4, // Number of related posts to display.
              'caller_get_posts'=> 1
          );
          $related_posts = new WP_Query($args);
          if( $related_posts->have_posts() ) {
              while ($related_posts->have_posts()) : $related_posts->the_post();
              get_template_part('templates/content','loop'); // The post item
              endwhile;
          }
          else{
              ?>
              <div class="col-sm-12"><?php _e('No related posts found.','themeaxe'); ?></div>
          <?php
          }
              wp_reset_query();
          ?>