Notify the user when their record is updated by an admin

pdb-update_notify.php

<?php
/*
  Plugin Name: Participants Database Update Notify
  Description: Notifies the user when their record is updated
 */
/*
 * before the update is stored, send an email notification to the participant
 */
add_filter( 'pdb-before_submit_update', 'pdb_send_record_update_notification' );

/**
 * sends an email notification when a record is updated
 * 
 * @param array $post the submitted record data
 * @return array the new record data
 */
function pdb_send_record_update_notification( $post )
{
  if ( ! is_admin() || empty( $post['email'] ) ) {
    /*
     * if we're not in the admin or if there is no email address to send to, do 
     * nothing and return
     */
    return $post;
  }
  /*
   * these three variables will need to be edited for your application
   */
  $subject = 'Your record has been updated';
  $message = 'Dear [first_name] [last_name],
    Your record has been updated.';
  $from = 'Your Website <info@yourwebsite.com>';
  /*
   * put it all together into the configuration array
   */
  $config = array(
      'to' => $post['email'],
      'from' => $from,
      'subject' => $subject,
      'template' => $message,
  );
  // send the email
  PDb_Template_Email::send( $config, $post );
  /*
   * return the record data so it can be saved
   */
  return $post;
}

hi sir,
I am working on a web application written in php & Mysql database and need to send a confirmation email to the user whenever the new event was approved by the admin. I used the above code but it is not working but there is no error showing. Can you please help me out. looking for your reply. Thanks.