Extend async I/O API by being able to pass other sockets

[thekid]

This makes it possible to asynchronously execute the following code:

$res->header('Content-Type', 'text/event-stream');
$res->header('Cache-Control', 'no-store');

$stream= $res->stream();

$s= new Socket('127.0.0.1', 8888);
$s->connect();
while (!$s->eof()) {

  // The following line will resume once the socket to become readable,
  // handling other requests while doing so!
  yield 'read' => $s;
  $bytes= addcslashes($s->read(), "\0..\37");

  $stream->write("event: message\n");
  $stream->write("data: Message {$bytes}\n\n");
  $stream->flush();
}

$s->close();
$stream->close();

Instead of a socket, we could imagine using Redis pub/sub with https://github.com/xp-forge/redis:

$sub= new RedisProtocol($dsn)->connect();
$sub->command('SUBSCRIBE', $channel);

$s= $sub->socket();
while (!$s->eof()) {
  yield 'read' => $s;
  [$type, $channel, $message]= $sub->receive();

  // TBI
}

This allows for low-level asynchronous processing. A more elaborate API may be implemented using https://wiki.php.net/rfc/fibers in the future, however, that would require PHP 8.1+, and we still support everything from 7.0 - 8.4!

[thekid]

Forward compatibility in the web API released in https://github.com/xp-forge/web/releases/tag/v3.12.0

[thekid]

Seeing weird timeout errors, including what might be a segfault: