<?php

// Replace the data compilation and output (ajax.php file) by this:

$images = array();
foreach ($media->data as $data) {
  $images[] = array(
    'id'    => $data->id,
    'url'   => $data->images->thumbnail->url,
    'user'  => $data->user->username
  );
}

echo json_encode(array(
  'next_id' => $media->pagination->next_max_id,
  'images'  => $images
));