Error Detection - Background Callback

Hello,

Thanks for this module. I like it :P ... I have a question about usage though. Say you have an asynchronous upload using the httprl_queue_background_callback() function. How would you detect errors that occur in that upload process? Errors that could include timeout, memory allocation, unable to write file? I've got my code in try / catch but sometimes it will just stop processing the files to upload and I don't see any reason why. An example of my code is below, I think I have as much error checking as I can. I've looked through your issues and examples of code usage and didn't see anything related to this. Your help is appreciated. Thank you.

<?php
if (!httprl_is_background_callback_capable()) {
  return FALSE;
}

// Example of background process     
$callback_options = array(
  array(
    'function' => 'example_upload_asynchronous',
      'options' => array(
         'timeout' => 1200,
         'global_timeout' => 1200,
       ),
    ),
    $file_attributes,
);
// Queue up the request.
httprl_queue_background_callback($callback_options);
// Execute request.
$response = httprl_send_request();
if ($response === FALSE) {
  return FALSE;
}

/**
 * Process the folder contents in the background.
 * @param $file_attributes
 */
function example_upload_asynchronous($file_attributes) {
  try {
    $error_uploading = FALSE;
    $dir = new RecursiveDirectoryIterator($file_attributes['full_path'], FilesystemIterator::SKIP_DOTS);
    // Flatten the recursive iterator, folders come before their files
    $it  = new RecursiveIteratorIterator($dir, RecursiveIteratorIterator::SELF_FIRST);
    // Basic loop displaying different messages based on file or folder
    foreach ($it as $fileinfo) {
      if (!$fileinfo->isDir()) {
        $full_path = $fileinfo->getPathname();
        if (strpos($full_path, 'Thumbs.db') !== FALSE || strpos($full_path, '.DS_Store') !== FALSE) {
          continue;
        }
        $path = str_replace($temp_path, '', $full_path);
        $bytes_written = file_put_contents($filename, $data);
        if ($bytes_written == NULL || $bytes_written == FALSE) {
          $error_uploading = TRUE;
          break;
        }
      }
    }
  }
  catch (Exception $e) {
    error_log("BAD UPLOAD EXCEPTION");
  }
}
?>