Update Post Meta on ACF Select Field

update_post_meta_acf.php

<?php
// Simple script used to touch/update post meta that was used in an Advanced Custom Fields select field that didn't have the reference field after an import of data thorugh a CSV. Running this script was enough to get the admin to dispaly the correct state that was already in the database.
require 'wp-config.php';
$things = get_posts(array('numberposts' => -1, 'post_type' => 'things')); // Change 'things' to the name of your post type
if (!$things) {
    echo 'No Posts';
    exit;
}
foreach ($things as $thing) {
    update_post_meta($thing->ID, "state", 'MN'); // 'state' was the name of the custom post meta ACF field.
    // add_post_meta($thing->ID, "_state", 'field_5a45552ee548e'); <-- Didn't need this when switching to update_post_meta but if you do need it this is the ACF reference field. Look for it in the database for reference.
}
echo 'Updated Things';