Related-post:

function rp_posts() {
    ob_start();
    echo '<section id="" class="widget widget_presscore-blog-posts">
        <div class="widget-title">SIMILAR POSTS</div>
    <ul class = "recent-posts"> ';
    ?>
    <?php
    $orig_post = $post;
    global $post;
    $categories = get_the_category($post->ID);
    if ($categories) {
        $category_ids = array();
        foreach ($categories as $individual_category)
            $category_ids[] = $individual_category->term_id;
        $args = array(
            'category__in' => $category_ids,
            'post__not_in' => array($post->ID),
            'posts_per_page' => 5, // Number of related posts that will be shown.
            'caller_get_posts' => 1
        );
        $my_query = new wp_query($args);
        if ($my_query->have_posts()) {
            //echo '<div id="related_posts"><ul>';
            while ($my_query->have_posts()) {
                $my_query->the_post();
                ?>
                <li>
                    <article class="post-format-standard">
                        <div class="wf-td">
                            <a class="alignleft post-rollover this-ready" href="<?php the_permalink() ?>">
                                <img class="preload-me" src="<?php the_post_thumbnail_url(array(60, 60)); ?>" width="60" height="60" alt="<?php the_title() ?>">
                                <i></i>
                            </a>
                        </div>
                        <div class="post-content">
                            <a href="<?php the_permalink() ?>">
                                <?php the_title() ?>                           
                            </a><br>
                            <time class="text-secondary" datetime="<?php the_time('F j, Y') ?>"><?php the_time('F j, Y') ?></time>
                        </div>
                    </article>
                </li>
                <?php
            }
        }
        $post = $orig_post;
        wp_reset_query();
        echo ' </ul>
</section>';
    }
}

add_shortcode('rp', 'rp_posts');
WordPress