Get category related posts published before given post

functions.php

<?php

/**
 * Class provided to get category related posts published before given post
 *
 * @author    Motivast motivast.com
 * @copyright 2018 - present, Motivast
 *
 * @license   https://www.gnu.org/licenses/old-licenses/gpl-2.0.txt GPL-2.0-or-later
 *
 * @link      https://gist.github.com/kierzniak/261a86c2172480f86228fd922eebcca2
 */

/**
 * Class provided to get category related posts published before given post
 */
class Motivast_Related_Posts {

	/**
	 * Current post id
	 *
	 * @var int
	 */
	private static $post_id;

	/**
	 * Get category related posts
	 *
	 * @param int   $post_id Current post id
	 * @param int   $limit   How many posts should be returned
	 *
 	 * @return array
	 */
	public static function get_category_related_posts( $post_id, $limit = 3 ) {

		$cats_ids = array();

		foreach( get_the_category( $post_id ) as $category ) {
			$cats_ids[] = $category->cat_ID;
		}

		self::$post_id = $post_id;

		add_filter( 'posts_where', 'Motivast_Related_Posts::only_get_posts_published_before_current_post' );

		$query = new WP_Query(array(
			'posts_per_page' => $limit,
			'category__in' => $cats_ids,
		));

		remove_filter( 'posts_where', 'Motivast_Related_Posts::only_get_posts_published_before_current_post' );

		return $query->posts;
	}

	/**
	 * Filter is used to add own pure SQL where clause to WP_Query SQL
	 *
	 * @param string $where Pure SQL where clause
	 * 
	 * @return string
	 */
	public static function only_get_posts_published_before_current_post( $where ) {

		global $wpdb;

		$where .= $wpdb->prepare( ' AND wp_posts.ID < %d', self::$post_id );

		return $where;
	}
}

/**
 * Get category related posts function
 *
 * @param int   $post_id Current post id
 * @param int   $limit   How many posts should be returned
 *
 * @return array
 */
function motivast_get_category_related_posts( $post_id, $limit = 3 ) {

	return Motivast_Related_Posts::get_category_related_posts( $post_id, $limit );
}