[Worpress] Add class to next/previous post links (Add class to links generated by next_posts_link & previous_posts_link)

wp-add-class-next_prev_post_links.php

<?php
/**
 * Add class to next/previous post links
 *
 * Add class to links generated by next_posts_link
 * and previous_posts_link
 */
if ( ! function_exists( 'posts_link_attributes_prev' ) || ! function_exists( 'posts_link_attributes_next' ) ) {

	function posts_link_attributes_prev() {
		return 'class="prev"';
	}
	function posts_link_attributes_next() {
		return 'class="next"';
	}

	add_filter('next_posts_link_attributes', 'posts_link_attributes_prev');
	add_filter('previous_posts_link_attributes', 'posts_link_attributes_next');

}