README

varion/minih2core-php is a minimal educational HTTP/2 core for PHP 8.1+.

This project is intentionally small and incomplete. It is designed for learning and demo servers, not production use.

Purpose

• Show how HTTP/2 frames can be encoded/decoded in a simple way.
• Provide a tiny server-side flow for one request stream and one response.
• Keep implementation readable without full RFC complexity.

Supported Frame Types (Minimal Subset)

• SETTINGS (basic ACK handling)
• PING (basic ACK handling)
• HEADERS (request stream detection, no header decoding)
• DATA (request end detection, response trigger)

The frame codec itself can encode/decode generic frame envelopes (9-byte header + payload).

Unsupported Features

• Full HTTP/2 compliance
• Request header decoding (HPACK decode)
• CONTINUATION handling
• Dynamic table (HPACK)
• Huffman encoding (HPACK)
• Flow control enforcement
• Stream prioritization / multiplexing
• Multi-stream request handling (demo is single-stream)
• Production-grade validation and error handling

Server Architecture

• Frame: immutable frame value object
• FrameCodec: binary frame encoder/decoder
• HpackEncoder: minimal response header block encoder
• ConnectionState: mutable per-connection state
• FrameHandler: tiny server-side state machine
• ResponseBuilder: creates HEADERS + DATA response frames

ReactPHP Example

See examples/react-http2-server.php.

What it does:

1. Accepts a TCP connection (h2c prior knowledge).
2. Reads and validates the HTTP/2 client preface.
3. Sends an empty server SETTINGS frame.
4. Buffers incoming bytes and repeatedly calls FrameCodec::tryDecode().
5. Passes each decoded frame to FrameHandler.
6. Encodes returned frames and writes them back.
7. Sends a single plain text response body: hello from http/2 server\n.
8. Closes the connection after the response.

Run example:

php examples/react-http2-server.php 8080

Test with curl:

curl -v --http2-prior-knowledge http://127.0.0.1:8080/

Client Architecture

The client example is also intentionally minimal and educational.

• ClientConnectionState: mutable state for one connection
• RequestBuilder: builds one GET request HEADERS frame on stream 1
• ClientFrameHandler: handles SETTINGS/ACK flow and minimal response events
• ClientConnection: ReactPHP connection wrapper around buffer/decode/write loop

Client Limitations

• client only
• HTTPS + ALPN(h2) only
• single GET request only
• one request stream only
• no response header decoding
• no HPACK decoder
• no CONTINUATION support
• no multiplexing / retries / flow-control enforcement
• small responses / demo only
• not production-ready

Client Example Flow

See examples/http2-client.php.

1. Parse [--insecure] <URI>.
2. Connect via TLS with ALPN h2,http/1.1.
3. Send client preface + empty SETTINGS.
4. Decode frames with FrameCodec::tryDecode().
5. On server SETTINGS, send SETTINGS ACK and one GET HEADERS frame.
6. Print DATA payload bytes to STDOUT.
7. Close on END_STREAM or GOAWAY.