Demonstrates how to set up a simple "with selected" action in the Participants Database admin record list.

pdb_set_records_payment_status.php

<?php
/*
 * Plugin Name: PDB Set Paid Status Tutorial
 * Version: 0.1
 * Description: Demonstrates how to set up a simple "with selected" action in the Participants Database admin record list.
 * Author: Roland Barker, xnau webdesign https://xnau.com
 * 
 */
/**
 * defines our action and adds it to the dropdown
 */
class PDb_Add_Payment_Status_Action {

  /**
   * @var string name of the action
   * 
   * this is used as the "key" to identify the action
   */
  private $action = 'set_paid_status';

  /**
   * sets up the filters and action handler
   */
  public function __construct()
  {
    add_filter( 'pdb-admin_list_with_selected_actions', array( $this, 'add_dropdown_actions' ) );
    add_filter( 'pdb-admin_list_with_selected_action_conf_messages', array( $this, 'set_confirmation_message' ) );
    add_action( 'pdb_admin_list_with_selected/' . $this->action, array( $this, 'do_operation' ) );
  }

  /**
   * adds the action to the dropdown
   * 
   * @param array $action_list list of the defined actions
   * @return array
   */
  public function add_dropdown_actions( $action_list )
  {
    // add the action with it's visible title as the key
    $action_list[ __( 'Mark as Paid' ) ] = $this->action;
    return $action_list;
  }

  /**
   * defines the confirmation message
   *
   * @param array $message_list list of confirmation messages
   * @return array
   */
  public function set_confirmation_message( $message_list )
  {
    // this message is going to accept a yes/no answer
    $message_list[ $this->action ] = array(
        "singular" => __( "Mark the selected record as paid?" ),
        "plural" => __( "Mark the selected records as paid?" ),
    );
    return $message_list;
  }

  /**
   * performs the operation on the selected records
   *
   * @param array $id_list list of all the selected record ids
   * @global wpdb $wpdb
   */
  public function do_operation( $id_list )
  {
    global $wpdb;
    foreach ( $id_list as $id ) {
      /*
       * this is where we change the value in the record
       */
      $wpdb->update( Participants_Db::$participants_table, array( 'payment_status' => 'paid' ), array( 'id' => $id ) );
      // note: this is inefficient for a very large list of ids to process
    }
  }

}
// instantiate our plugin class here
new PDb_Add_Payment_Status_Action();