Updates to ActivityPub in a single PHP file

A few weeks ago, I built an ActivityPub Server in a Single PHP File. It's a proof of concept showing how easy it is to turn a website into a full-featured Fediverse participant.

After a bunch of feedback and testing, I've added a some features to make it slightly more useful.

  • A single PHP file - 45KB of no-library goodness. Just add your details, upload, and done.
  • No databases. Everything stored as JSON files on disk.
  • Be followed. External users can discover and follow you.
  • Send messages. You can send messages to all your followers.
  • 🆕 Follow users. You can follow other Fediverse actors.
  • 🆕 Read messages. You can read the messages sent to your Inbox. If media is attached, those will be displayed.
  • 🆕 Verify signatures. ActivityPub messages can by cryptographically signed. This now verifies those signatures.

You can grab the code here - pull requests welcome. If you want to see what it looks like in action, visit https://example.viii.fi/ or follow @example@example.viii.fi.

Again, to re-emphasise what it says in the README - this is not suitable for production use. This is primarily a way to explain all the different functions of an ActivityPub server. It is adequately commented and I hope a moderately competent programmer could follow what's going on. It is almost certainly insecure and is considered harmful to aquatic life.

I would be delighted if you took the code and did something interesting with it. Perhaps create a single-file server in your favourite language?


A few random things which I might add - or which you might consider making and sending a Pull Request:

  • Better UI. It is deliberately bare-bones, see the /read interface. But perhaps there's a simpler way to make it look nice?
  • No threading in the UI - and no ability to reply to messages.
  • Support for reading hashtagged posts on the site.
  • Reply highlighting - at the moment you can't see if a message was sent to you.
  • Some Fediverse posts contain polls, content warnings, and other extended features. That could be fun to support - both for reading and writing.
  • Support for reading custom emoji.
  • Deletes, Updates, and Undos are received - but it currently doesn't remove the previously saved file.
  • There's no way to unfollow a user - except for manually deleting data from the file-system.
  • Only supports one image upload. Could support more? Or even other media?
  • I don't think CC works properly.
  • Message visibility could be useful.
  • Boring stuff like better error handling.

If you have opinions, please let me know!

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