Shows how to set a custom filename for an uploaded image

pdb-custom-image-filename.php

<?php
/**
 * Plugin Name: PDB Custom Image Filename
 * Description: names an uploaded image file according to other values in the record
 * Version: 1.0
 */

// attach the handler function to the filter
add_action( 'pdb-file_upload_filename', 'pdb_set_custom_filename', 10, 3 );
  

/**
 * sets the custom filename
 *
 * @filter pdb-file_upload_filename
 * @param string $filename the sanitized filename (without extension)
 * @param PDb_Form_Field_Def $field_definition the field definition parameters
 * @param int|bool $record_id the record id or bool false if the ID hasn't been determined yet (as in a signup form)
 * @return string filename without its extension
 */
function pdb_set_custom_filename( $filename, $field_definition, $record_id )
{
  // first check to see that we're going to modify the correct image upload field
  // the field name of the image we want to modify is "profile_picture"
  if ( $field_definition->name() === 'profile_picture' ){
    
    // get the current record data
    // this assumes the image upload is taking place after the record has been 
    // saved, in other words, not during a signup submission
    $record = Participants_Db::get_participant($record_id);
    
    // make the filename
    $filename = strtolower( $record['first_name'] . '-' . $record['last_name'] );
  }
  
  return $filename;
}