Wordpress Related Posts function

functions.php

<?php

/**
 * Related Posts.
 *
 * Usage:
 * To show related by categories:
 * Add in single.php <?php dfw_related_posts(); ?>.
 * To show related by tags:
 * Add in single.php <?php dfw_related_posts('tag'); ?>.
 *
 * @global array $post
 *   WP global post.
 * @param string $display
 *   Set category or tag.
 * @param int $qty
 *   Number of posts to be displayed.
 * @param bool $images
 *   Enable or disable displaying images.
 * @param string $title
 *   Set the widget title.
 */
function dfw_related_posts($display = 'category', $qty = 5, $images = true, $title = 'Artigos Relacionados') {
    global $post;

    $show = false;
    $post_qty = (int) $qty;

    switch ($display) :
        case 'tag':
            $tags = wp_get_post_tags($post->ID);

            if ($tags) {
                $show = true;
                $tag_ids = array();
                foreach ($tags as $individual_tag) {
                    $tag_ids[] = $individual_tag->term_id;
                }

                $args = array(
                    'tag__in' => $tag_ids,
                    'post__not_in' => array($post->ID),
                    'posts_per_page' => $post_qty,
                    'ignore_sticky_posts' => 1
                );
            }
            break;

        default :
            $categories = get_the_category($post->ID);

            if ($categories) {
                $show = true;
                $category_ids = array();
                foreach ($categories as $individual_category) {
                    $category_ids[] = $individual_category->term_id;
                }

                $args = array(
                    'category__in' => $category_ids,
                    'post__not_in' => array($post->ID),
                    'showposts' => $post_qty,
                    'ignore_sticky_posts' => 1
                );
            }
    endswitch;

    if ($show == true) {
        $related = new wp_query($args);
        if ($related->have_posts()) {
            $layout = '<div id="related-post">';
            $layout .= '<h3>' . strip_tags($title) . '</h3>';
            $layout .= '<ul>';

            while ($related->have_posts()) {
                $related->the_post();

                $layout .= '<li>';

                if ($images == true) {
                    $layout .= '<span class="thumb">';
                    $layout .= '<a href="' . get_permalink() . '" title="' . get_the_title() . '">' . get_the_post_thumbnail() . '</a>';
                    $layout .= '</span>';
                }

                $layout .= '<span class="text">';
                $layout .= '<a href="' . get_permalink() . '" title="' . get_the_title() . '">' . get_the_title() . '</a>';
                $layout .= '</span>';

                $layout .= '</li>';
            }

            $layout .= '</ul>';
            $layout .= '</div>';

            echo $layout;
        }
        wp_reset_query();
    }
}

?>