// use get_queried_object because you might not be showing
// something that returns an value for get_queried_object_id()
$queried_object = get_queried_object();
// initialize $persons in case nothing is returnd for field
$persons = false;
// test queried object to see if it's a post
if (is_a($queried_object, 'WP_POST')) {
$persons = get_field('persons', $queried_object->ID);
}
// test $persons to make sure something was returned
if (!empty($persons)) {
foreach ($persons as $post) {
setup_postdata($post);
?><meta name="author" content="<?php the_title() ?>" /><?php
}
wp_reset_postdata();
}
// if nothing was returned for $persons show a default
// if this is a single post
if (!$persons && is_single()) {
?><meta name="author" content="<?php echo get_the_author_meta('display_name', $post->post_author); ?>"><?php
}
