While symlink() isn't supported by PHP Stream Wrappers to create symlinks, you can still interact with symlinks that already exist.

<?php
use Vfs\FileSystemBuilder;
use Vfs\Node\FileLink;

$fs = (new FileSystemBuilder())->setTree(['foo' => ['bar' => 'baz']])->build();
$fs->get('/')->add(new FileLink('my_symlink', $fs->get('/foo/bar')));

is_link('vfs://my_symlink'); // => true

They're actually implemented as hard links rather than symbolic links, meaning that if the target file is moved or renamed the link still works. It was easier to implement this way.