Demonstrates how to load a "Chosen" dropdown with options in Participants Database

pdb-populate-chosen-selector.php

<?php
/**
 * Plugin Name: PDB Populate Chosen Dropdown
 * Description: tests loading a chosen element with options
 *
 * sets our function to be called when the pdbcde-before_element_rendered action 
 * is triggered by the form just before the "Chosen Dropdown" is shown so we can 
 * change the list of options to show
 */
 
// attach our function to the pdbcde-before_element_rendered action
add_action( 'pdbcde-before_element_rendered', 'xnau_set_specialty_dropdown_options');

// this is needed when using a Chosen dropdown/other element
add_action( 'pdb-form_element_build_chosen-dropdown-other', 'xnau_set_specialty_dropdown_options');

/**
 * sets the options for the "specialty" dropdown
 *
 * @global wpdb $wpdb
 * @param PDb_FormElement object $field the current field
 */
function xnau_set_specialty_dropdown_options ( $field )
{
  // this is the name of the field we want to add options to
  $fieldname = 'specialty';
 
  if ( $field->name === $fieldname ) :  // check for our dropdown field
  
  global $wpdb; // grab the db helper object
  
  /*
   * define the query for getting the list saved specialties
   * 
   * note that the $wpdb->prefix method is used to get the table 
   * prefix; this is so it will work on all WP installs
   */
  $query = '
    SELECT DISTINCT `' . $fieldname . '`
    FROM ' . $wpdb->prefix . 'participants_database 
  ';
  
  // now execute the query and get the results
  $raw_names = $wpdb->get_results( $query );
  
  /*
   * now expand the result array into an array for the options 
   * property of the dropdown
   */
  $options = $field->options;
  foreach ( $raw_names as $record ) {
    
    // this is the value we'll be considering
    $new_value = $record->{$fieldname};
   
    /*
     * check the value against the defined options so we only 
     * add options that are not already in there
     */
    if ( ! in_array( $new_value, $options ) ) {
      // it's a new value, so add it to the dropdown options
      $options[$new_value] = $new_value;
    }
  }
  
  // now set the field object with the new options list
  $field->options = $options;
  
  endif;
}