acme 
kelunik/acme is a non-blocking implementation of the ACME protocol based on the amp concurrency framework.
If you're looking for a PHP client, have a look at
kelunik/acme-clientwhich is based on this library.
Required PHP Version
- PHP 7.0
Installation
composer require kelunik/acmeThis package follows semantic versioning. Although there's no v1.0.0 yet, it's safe to use it as a dependency, because breaking changes won't be installed when using it as ^0.3.
The library is fully documented using PHPDoc.
Usage
If you're not familiar with promises and amphp/amp yet, read my blog post to get started.
You can always use Amp\Promise\wait to use this async library in synchronous code.