related posts

relatedposts.php

<?php
/**
 * Get category IDs of current post.
 */
function bt_get_current_post_category_ids($post_id) {
	$cat_ids = wp_get_post_categories( $post_id, array('fields' => 'ids') );

	if (empty($cat_ids) || is_wp_error($cat_ids)) {
		return array();
	} 

	if (!is_array($cat_ids)) {
		$cat_ids = array($cat_ids);
	}

	return $cat_ids;
}

/**
 * Get tag IDs of current post.
 */
function bt_get_current_post_tag_ids($post_id) {
	$tag_ids = wp_get_post_tags( $post_id, array('fields' => 'ids') );

	if (empty($tag_ids) || is_wp_error($tag_ids)) {
		return array();
	} 

	if (!is_array($tag_ids)) {
		$tag_ids = array($cat_ids);
	}

	return $tag_ids;
}

/**
 * Query related posts.
 */
function bt_query_related_posts($post_id, $num = 3) {
	$args = array(
		'post_type' => 'post', 
		'post_status' => 'publish', 
		'showposts' => $num,
		'orderby' => 'date', 
		'order' => 'desc',
		'post__not_in' => array($post_id)
	);

	$tag_ids = array();
	$cat_ids = array();

	if (get_post_type($post_id) == 'post') {
		$cat_ids = bt_get_current_post_category_ids($post_id);
		$tag_ids = bt_get_current_post_tag_ids($post_id);
	}

	if (!empty($cat_ids) || !empty($tag_ids)) {
		$args['tax_query'] = array(
			'relation' => 'OR'
		);

		if (!empty($tag_ids)) {
			$args['tax_query'][] = array(
				'taxonomy' => 'post_tag',
				'field' => 'term_id',
				'terms' => $tag_ids
			);
		}
		
		if (!empty($cat_ids)) {
			$args['tax_query'][] = array(
				'taxonomy' => 'category',
				'field' => 'term_id',
				'terms' => $cat_ids,
				'include_children' => false
			);
		}
		
		return new WP_Query($args);
	}

	return false;		
}

/**
 *  Usage in single.php or template part.
 */
$related = bt_query_related_posts($post->ID, 3); 
if ($related && $related->have_posts()) :
?>
<div>
	<h4><?php _e('Related Articles'); ?></h4>
	<div class="row">
		<?php while ($related->have_posts()) : $related->the_post(); ?>
		<div class="col col-md-8">
			<?php if (has_post_thumbnail()) : ?>
			<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
				<?php the_post_thumbnail(); ?>
			</a>
			<?php endif; ?>
			<div class="post-meta">
				<span class="post-categories"><?php the_category(', '); ?></span>
				<span class="post-date"><?php the_time('F j, Y'); ?></span>
			</div>
			<h3><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>
		</div>
		<?php endwhile; ?>
	</div>
</div>
<?php
wp_reset_postdata();
endif;

What is this code meant for? I want to show related post on my blog without using a plugin. I am using Genesis Framework.