ahnlak on Nostr: In a bid to avoid re-inventing the wheel, does there exist a PHP library to add ...

In a bid to avoid re-inventing the wheel, does there exist a PHP library to add ActivityPub functionality *to an existing website*?

There are a handful of 'concept demos' and even a few full PHP implementations of an ActivityPub server, but nothing (that I've found) that is just a drop-in component to allow, say, an existing website to post content / updates from itself.