Shows how to route the Participants Database signup notification email to a recipient based on a value in the submission

pdb-select-email-recipient.php

<?php

/*
 * Plugin Name: Participants Database Custom Signup Email Recipient
 * Version: 0.1
 * Description: sets the signup notification email recipient based on a value in the signup submission
 * Author: Roland Barker, xnau webdesign http://xnau.com
 * 
 */

class pdb_select_email_recipient {
  
  /**
   * @var string name of the selector used to determine the routing
   * 
   * edit this to match the name of the selector you are using
   */
  private $router = 'department';
  
  /**
   * initializes the class
   */
  public function __construct()
  {
    add_action( 'pdb-before_signup_thanks', array( $this, 'assign_recipient' ) );
  }
  
  /**
   * checks the submission to determine the recipient of the email
   * 
   * @see https://xnau.com/work/wordpress-plugins/participants-database/participants-database-documentation/participants-database-api/#bst
   * 
   * @param object $thanks
   */
  public function assign_recipient( $thanks )
  {
    // get the value of the router field
    $selection = $thanks->participant_values[$this->router];
    
    // defaults to the notification recipient as defined in the email template
    $recipient = $thanks->notify_recipients;
    
    // choose the notification recipient according to the selection
    switch ( $selection ) {
      
      case 'sales':
      case 'returns':
        $recipient = 'Andrea Sales <andrea@xnaucorp.com>';
        break;
      
      case 'support':
        $recipient = 'Jaime Support <support@xnaucorp.com>';
        break;
      
      case 'jobs':
        $recipient = 'Gregory Jobs <jobs@xnaucorp.com>';
        break;
        
    }
    
    // set the recipient of the signup notification
    $thanks->notify_recipients = $recipient;
  }

}

new pdb_select_email_recipient;

Check this article for the full run-down...

Sending a Signup Notification to a Custom Recipient