demonstrates how to reset the private ID after it is used to open a record edit page

pdb-one-time-use-pid.php

<?php
/*
 * 3-20-17 updated to run on pdb-before_submit_update filer
 *
 */
add_filter( 'pdb-before_submit_update', 'pdb_otu_regenerate_pid' );

/**
 * regenerates the private id for the current record
 * 
 * @param array  $post the posted data
 * @return  array the post data
 */
function pdb_otu_regenerate_pid( $post )
{
  // check if the record ID is already in the session
  $record_id = Participants_Db::$session->get('pdbid');
  if (
          ! is_admin() &&
          ! $record_id
  ) {
    global $wpdb;
    $wpdb->update(
      Participants_Db::$participants_table, 
      array('private_id' => Participants_Db::generate_pid() ), 
      array('id' => $post['id'])
    );
    /* 
     * this is so the user will continue to have access to the record page and 
     * the private ID won't get renewed again
     */
    Participants_Db::$session->set( 'pdbid', $post['id'] );
  }
  return $post;
}