Shows how to update Participants Database calculated field using a cron.

pdb-dynamicfield-cron-updater.php

<?php
/**
 * Plugin Name: PDB Dynamic Field Cron Updater
 * Description: updates dynamic fields automatically on a WP cron
 * Version: 1.0
 */

class PDb_Dynamicfield_Cron_Updater
{
  
  /**
   * @param string name of the cron hook
   */
  private $hook = 'xnau_dynfield_update';
  
  /**
   * sets up the cron and actions
   */
  public function __construct()
  {
    // use this function to reset the cron
    // useful if you need to change the time it runs
    // remember to comment it out again after
    //$this->unschedule();
    
    // this sets up the method that is called when our cron runs
    add_action( $this->hook, [$this,'dynamic_db_field_update'] );
    
    /*
     *  this sets the daily cron time to 12pm
     * 
     *  IMPORTANT: normally, the WP cron is run when someone visits the site, 
     *  therefore if your site is not getting much traffic, the cron probably 
     *  won't run on time.
     * 
     *  There are many examples of how to set up the WP cron to run without 
     *  needing the site visit to trigger it, for example:
     *  https://www.siteground.com/tutorials/wordpress/real-cron-job/
     */
    $time_of_day = strtotime('2024-02-07 12:00:00');
    
    if ( ! wp_next_scheduled( $this->hook ) )
    {
      // this sets up the WP cron to trigger our action daily at the time set above
      wp_schedule_event( $time_of_day, 'daily', $this->hook );
    }
  }
  
  /**
   * update a dynamic db field value
   * 
   * this will process an update for all dynamic fields for all records
   */
  public function dynamic_db_field_update()
  {
    $id_list = Participants_Db::get_id_list([]); // gets all record ids
    
    foreach( $id_list as $id )
    {
      $record = Participants_Db::get_participant( $id );
      
      if ( ! is_array( $record ) )
      {
        // if the id doesn't pull up a record, skip to the next one
        continue;
      }
       
      $this->update_record( $record );
    }
  }
  
  /**
   * updates a new record
   * 
   * @param array $record the new record submission values
   */
  private function update_record( $record )
  {
    // update the dynamic values in the record
    $updated_record = apply_filters( 'pdb-dynamic_db_field_update', $record );
    
    // filter out any values that did not change
    $post = array_diff_assoc( $updated_record, $record );
    
    if ( ! empty( $post ) )
    {
      // if we have changed values, write them to the database
      Participants_Db::write_participant( $post, $record['id'] );
    }
  }
  
  /**
   * unschedules the cron
   */
  private function unschedule()
  {
    $timestamp = wp_next_scheduled( $this->hook );
    wp_unschedule_event( $timestamp, $this->hook );
  }
}

new PDb_Dynamicfield_Cron_Updater();