A function to output a delimited list of posts given an array of IDs in WordPress

wordpress_posts_list.php

<?php
/**
 * Make a list of links to WordPress posts
 * 
 * Works great with the Relationship field from Advanced Custom Fields
 * 
 * @param array $posts array of post objects or post_ids
 * @param string $sep separater
 * @param string $before output before the list
 * @param string $after output after the list
 * @param bool $links whether to link titles to posts, default = true
 * @param 'objects'|'ids' $type whether the $posts param contains objects or IDs. Default: 'objects'
 * @return string links separated by commas
 */
function ciswa_posts_list( $posts, $sep = ', ', $before = '', $after = '', $links = true, $type = 'objects' ) {
  if( ! $posts && ! is_array( $posts ) )
		return; // nothing to do

	if( $type = 'objects' ) {
		$posts = wp_list_pluck( $posts, 'ID' );
	}

	$post_links = array();
	if( (bool) $links ) {
		foreach ($posts as $key => $id) {
			$post_links[] = '<a href="' . esc_url( get_permalink( $id ) ) . '">' . esc_attr( get_the_title( $id ) ) . '</a>';
		}
	} else {
		foreach ($posts as $key => $id) {
			$post_links[] = esc_attr( get_the_title( $id ) );
		}
	}

	return $before . implode( $sep, $post_links ) . $after;
}