Shows how to set up a Participants Database email that will automatically send when conditions are met

pdb-email-cron.php

<?php

/**
 * Plugin Name: PDB Email Cron
 * Plugin URI:  https://xnau.com/?p=7354
 * Description: Provides a basic framework for setting up an automated Participants Database email send
 * Version:     1.0
 * Author:      xnau webdesign
 * Author URI:  https://xnau.com
 * License:     GPL2
 * License URI: https://www.gnu.org/licenses/gpl-2.0.html
 */

/*
 * to use this plugin, you must have the Participants Database Email Expansion Kit 
 * plugin installed and you must define an email template to use. The ID of that 
 * template must be typed in where the value of the $template_id property is set.
 */

class PDB_Email_Cron {

  /**
   * @var string name of the cron event
   */
  const event = 'pdb_email_cron';

  /**
   * @var int ID of the Participants Database email template to use
   *
   * you must change the value here to the ID of the email template you want to use
   */
  private $template_id = 9797;

  /**
   * @var string name of the option to use to keep the send logs
   */
  const send_log = 'pdb_email_cron_send_log';

  /**
   * initializes the plugin
   */
  public function __construct()
  {
    add_action( self::event, array($this, 'check_reminders') );

    register_activation_hook( __FILE__, array(__CLASS__, 'activate') );
    register_deactivation_hook( __FILE__, array(__CLASS__, 'deactivate') );
    register_uninstall_hook( __FILE__, array(__CLASS__, 'uninstall') );
  }

  /**
   * checks for records that need an email sent
   */
  public function check_reminders()
  {
    // first, get a list of all accounts that have not checked in for the last 30 days
    $late_accounts = $this->get_late_accounts();

    // check each one to see if it needs to get an email sent
    foreach ( $late_accounts as $record ) {
      // check these against the send log so we don't keep sending notices
      if ( $this->email_should_be_sent( $record['id'] ) ) {
        $this->send_reminder( $record );
      }
    }
  }

  /**
   * sends the email
   * 
   * @param array $record array of record data for the template
   * 
   */
  private function send_reminder( $record )
  {
    // we need an instance of the email template to send with the action
    $template = new cpt_email_templates\template($this->template_id);
    
    // this action triggers sending the email using the record data and the selected email template
    // UNCOMMENT THE NEXT LINE WHEN YOU KNOW YOU ARE READY TO START SENDING EMAILS
    //do_action( 'pdbcptet-action_send_email', $template, $record, 'PDB Email Cron' );
    
    /*
     * this is where you would put an error_log statement to see what email would be sent
     * for example:
     * error_log(__METHOD__.' sending email to record: ' . $record['id']);
     */

    // log the send so we can prevent duplicate notices
    $this->log_send( $record['id'] );
  }

  /**
   * check if an email was sent to an account in the last 7 days
   * 
   * @param int $record_id
   * @return bool true if the email should be sent
   */
  private function email_should_be_sent( $record_id )
  {
    $send_list = get_option( self::send_log );
    
    if ( !$send_list ) {
      $send_list = array();
    }

    if ( !array_key_exists( $record_id, $send_list ) ) {
      // email to this account has never been sent
      return true;
    }

    $last_send_date = $send_list[$record_id];

    if ( $last_send_date < strtotime( '-7 days' ) ) {
      // it's been over a week, send it again
      return true;
    }

    // an email was sent to this account in the last week; don't send
    return false;
  }

  /**
   * logs the send
   * 
   * @param int $record_id
   */
  private function log_send( $record_id )
  {
    $send_list = get_option( self::send_log );
    
    if ( ! $send_list ) {
      $send_list = [];
    }

    $send_list[$record_id] = time(); // log the timestamp of the sent email

    update_option( self::send_log, $send_list );
  }

  /**
   * queries the db for late accounts
   * 
   * @global wpdb $wpdb
   */
  private function get_late_accounts()
  {
    global $wpdb;

    // looking for records that have a last_accessed date of over 30 days ago
    $late_date = date( 'Y-m-d G:i:s', strtotime( '-30 days' ) ); // 30 days ago

    $sql = 'SELECT * FROM ' . Participants_Db::$participants_table . ' WHERE last_accessed < "' . $late_date . '" ';

    $result = $wpdb->get_results( $sql, ARRAY_A );
    
    return $result;
  }

  /**
   * initializes the cron
   */
  public static function activate()
  {
    wp_schedule_event( time(), 'daily', self::event );
  }

  /**
   * clears the cron
   */
  public static function deactivate()
  {
    wp_clear_scheduled_hook( self::event );
  }

  /**
   * removes the plugin
   */
  public static function uninstall()
  {
    delete_option( self::send_log );
  }

}

new PDB_Email_Cron;