Synchronize / connect WordPress Post Author field with Advanced Custom Fields (ACF) user field

sync_acf_field_with_post_author

<?php
function mve_save_task_post_hook($post_id, $post, $update) {
    if ($post->post_type != 'task') {
        return;
    }

    // If ACF Customer != Post author, update it
    $old_post_author = sanitize_text_field($_REQUEST['post_author']);
    $new_post_author = sanitize_text_field($_REQUEST['post_author_override']);
    if (isset($new_post_author) &&
        $old_post_author != $new_post_author
    ) {
        remove_action("acf/update_value/name=customer", "mve_save_task_update_author_acf_hook");

        update_field("customer", $new_post_author);

        add_filter('acf/update_value/name=customer', 'mve_save_task_update_author_acf_hook', 10, 3);
    }
}
add_action('save_post', 'mve_save_task_post_hook', 10, 3);

function mve_save_task_update_author_acf_hook( $customer_id, $post_id, $field  ) {
    // Author ACF field changed
    if ($customer_id != get_field('customer')["ID"]) {
        $my_post = array(
            'ID' => $post_id,
            'post_author' => $customer_id
        );

        remove_action('save_post', 'mve_save_task_post_hook');

        // Update the post into the database
        wp_update_post($my_post);

        add_action('save_post', 'mve_save_task_post_hook', 10, 3);
    }

    return $customer_id;
}
add_filter('acf/update_value/name=customer', 'mve_save_task_update_author_acf_hook', 10, 3);