<?php
require 'vendor/autoload.php';
$openstack = new OpenStack\OpenStack([
 'authUrl' => '{authUrl}',
 'region' => '{region}',
 'user' => [
 'id' => '{userId}',
 'password' => '{password}'
 ],
 'scope' => ['project' => ['id' => '{projectId}']]
]);
/** @var \GuzzleHttp\Stream\Stream $stream */
$stream = $openstack->objectStoreV1()
 ->getContainer('{containerName}')
 ->getObject('{objectName}')
 ->download();
file_put_contents('my_dest_file.bin', $stream->getContents());