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PHP Libraries

PHP libraries for implementing ActivityPub.

ActivityPub for WordPress​

Official WordPress ActivityPub plugin.

PropertyValue
Repositorygithub.com/Automattic/wordpress-activitypub
LicenseMIT
StatusActive

Features​

  • WordPress integration
  • Automatic actor creation
  • Post federation
  • WebFinger support

Usage​

Install via WordPress plugins, then configure in Settings → ActivityPub.

ActivityPhp​

ActivityPub/ActivityStreams library.

PropertyValue
Repositorygithub.com/landrok/activitypub
Packagistlandrok/activitypub
LicenseMIT
StatusActive

Example​

use ActivityPhp\Type;
use ActivityPhp\Server\Server;

// Create a Note
$note = Type::create('Note', [
    'id' => 'https://example.com/notes/123',
    'content' => 'Hello from PHP!',
    'attributedTo' => 'https://example.com/users/alice'
]);

echo json_encode($note->toArray(), JSON_PRETTY_PRINT);

Server Implementation​

use ActivityPhp\Server\Server;

$server = new Server([
    'instance' => [
        'host' => 'example.com',
        'port' => 443,
    ],
    'actor' => [
        'preferredUsername' => 'alice'
    ]
]);

// Handle incoming activity
$server->inbox()->handle($request);

Pixelfed Source​

Reference for Laravel-based implementation.

PropertyValue
Repositorygithub.com/pixelfed/pixelfed
Key Pathsapp/Util/ActivityPub/, app/Services/

Notable Patterns​

pixelfed/
├── app/Util/ActivityPub/
│   ├── Inbox.php          # Inbox handling
│   ├── Outbox.php         # Outbox handling
│   ├── HttpSignature.php  # Signing
│   └── Helpers.php        # Utilities
├── app/Services/
│   └── ActivityPubFetchService.php

phpseclib​

RSA cryptography for HTTP Signatures.

PropertyValue
Repositorygithub.com/phpseclib/phpseclib
Packagistphpseclib/phpseclib
StatusActive

HTTP Signature Signing​

use phpseclib3\Crypt\RSA;

function signRequest($privateKeyPem, $keyId, $method, $path, $headers, $body) {
    $privateKey = RSA::loadPrivateKey($privateKeyPem);

    // Build signing string
    $signingParts = [];
    $signingParts[] = "(request-target): " . strtolower($method) . " " . $path;
    $signingParts[] = "host: " . $headers['Host'];
    $signingParts[] = "date: " . $headers['Date'];
    $signingParts[] = "digest: SHA-256=" . base64_encode(hash('sha256', $body, true));

    $signingString = implode("\n", $signingParts);

    // Sign
    $signature = $privateKey->sign($signingString);

    return sprintf(
        'keyId="%s",algorithm="rsa-sha256",headers="(request-target) host date digest",signature="%s"',
        $keyId,
        base64_encode($signature)
    );
}

json-ld (PHP)​

JSON-LD processor.

PropertyValue
Repositorygithub.com/lanthaler/JsonLD
Packagistml/json-ld
StatusStable

Example​

use ML\JsonLD\JsonLD;

// Expand
$expanded = JsonLD::expand($document);

// Compact
$compacted = JsonLD::compact(
    $expanded,
    'https://www.w3.org/ns/activitystreams'
);

Laravel Integration​

Actor Controller​

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class ActorController extends Controller
{
    public function show($username)
    {
        $user = User::where('username', $username)->firstOrFail();

        return response()->json([
            '@context' => [
                'https://www.w3.org/ns/activitystreams',
                'https://w3id.org/security/v1'
            ],
            'type' => 'Person',
            'id' => route('actor', $username),
            'preferredUsername' => $user->username,
            'inbox' => route('inbox', $username),
            'outbox' => route('outbox', $username),
            'publicKey' => [
                'id' => route('actor', $username) . '#main-key',
                'owner' => route('actor', $username),
                'publicKeyPem' => $user->public_key
            ]
        ], 200, [
            'Content-Type' => 'application/activity+json'
        ]);
    }
}

Inbox Handler​

public function inbox(Request $request, $username)
{
    // Verify HTTP Signature
    $this->verifySignature($request);

    $activity = json_decode($request->getContent(), true);

    switch ($activity['type']) {
        case 'Follow':
            $this->handleFollow($activity);
            break;
        case 'Create':
            $this->handleCreate($activity);
            break;
        case 'Undo':
            $this->handleUndo($activity);
            break;
    }

    return response('', 202);
}

Comparison​

LibraryFrameworkCompleteness
ActivityPub for WordPressWordPressPlugin
ActivityPhpAnyComprehensive
Pixelfed sourceLaravelReference

Recommendations​

For WordPress: Use the official plugin.

For Laravel: Study Pixelfed patterns.

For other PHP: Use ActivityPhp.

See Also​