Displaying links to all posts of the same category on the post page

Question

I want to display the links to all posts of the same category of the current post on that page. I wrote the following code in the single.php file.

<?php $categories_of_this_post = get_the_category(); ?>
<?php $fist_category_id = $categories_of_this_post['0']->term_id; ?>
<?php $this_post_ID = get_the_ID(); ?>
<div class="related-posts">
    <ol>
    <?php query_posts( array ( 'cat' => $fist_category_id, 'orderby' => 'date', 'order' => 'ASC' ) ); ?>
    <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
        <li>
            <?php if (get_the_ID() != $this_post_ID) : ?>
            <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
            <?php else : ?>
            <?php the_title(); ?>
            <?php endif; ?>
        </li>
    <?php endwhile; else: ?>
    <p><?php _e('Sorry, no articles written under this category.'); ?></p>
    <?php endif; ?>
    </ol>
</div>

But this code returns all the posts found on the WordPress website. Where it goes wrong?

Answer 1

I've not tested this, but the following is the method you shoulduse. Don't use query_posts.

 $cats_of_post= get_the_category();

 if($cats_of_post){
      $cat_id = (int) $cats_of_post['0']->term_id;
      $related = get_posts(array(
           'numberposts'     => 5,
           'category'        => $cat_id,
           'orderby'         => 'post_date',
           'order'           => 'DESC',
           'exclude'         =>
       ));

       global $post;
       $temp_post = $post;?>

       <div class="related-posts">

       <?php if( $related ): ?>
               <ol>
               <?php foreach ($related as $post): ?>
                    <li>
                         <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
                    </li>
                <?php endforeach; ?>

       <?php else: //No posts ?>
            <p><?php _e('Sorry, no articles written under this category.'); ?></p>

       <?php endif; ?>
       <?php $post = $temp_post; ?>
       </div>
<?php }//Endif no $cats_of_post