Recursively iterate through trigger tree options

Recursive SQL for Triggers

/**
 * get_joined_meta - Recursively gets and builds a JSON compatible array of all of the selected trigger options to dynamically build trigger events
 *
 * @param string $meta_id: The string for checking the meta_id of the trigger. Default: "is null"
 *
 * @returns array: The compiled list of nested options for a trigger meta item in JSON format. 
 */
public function get_joined_meta($meta_id = "is null")
{
  /** get the global db connection */
  global $wpdb;
  $return_results = array();
  $query="SELECT * from wp_command_triggermeta WHERE meta_id $meta_id";
  $results = $wpdb->get_results($query);

  if(!empty($results))
  {
    /** Iterate through results and build the return array */
    foreach($results as $result)
    {
      $return_results[$result->meta_key][$result->id] = array('value' =>$result->meta_value);
      /** Call this function again */
      $sub_results = $this->get_joined_meta("= ". $result->id);
      $keys = array_keys($sub_results);
      foreach($keys as $key)
      {
        $return_results[$result->meta_key][$result->id][$key] = $sub_results[$key];
      }
    }
  }
  return $return_results;
}