Do not report `AcceptFailed` when timing out in `stream_socket_accept()` for non-blocking listeners

Start at the implementation behind stream_socket_accept() and trace how a non-blocking listener with a zero timeout records stream errors. Reproduce the issue with the provided PHP script, then find the relevant stream socket tests and add coverage for the expected no-error result while preserving genuine accept failures.

Description

The following code:

<?php

$server = stream_socket_server(
    'tcp://127.0.0.1:0',
    context: stream_context_create([
        'stream' => [
            'error_mode' => StreamErrorMode::Silent,
            'error_store' => StreamErrorStore::All,
        ],
    ]),
);
stream_set_blocking($server, false);
var_dump(stream_socket_accept($server, 0));

foreach (stream_last_errors() as $error) {
    var_dump($error);
}

Resulted in this output:

bool(false)
object(StreamError)#3 (5) {
  ["code"]=>
  enum(StreamErrorCode::AcceptFailed)
  ["message"]=>
  string(35) "Accept failed: Connection timed out"
  ["wrapperName"]=>
  string(6) "stream"
  ["severity"]=>
  int(2)
  ["terminating"]=>
  bool(true)
}

But I expected this output instead:

bool(false)

While it is technically true that accepting a new connection failed, no clients waiting is an expected situation when using a non-blocking listener socket (in particular with a zero-timeout). It is a common pattern to call accept() until no more client connections are returned to quickly drain the listening queue after the polling API marked the listener as readable instead of sending it through the whole polling logic again.

By treating the timeout as a failure with the generic AcceptFailed error code, it becomes impossible to distinguish this situation from genuine failures (such as exhausted file descriptors) without inspecting the message, which is particularly annoying when combined with StreamErrorMode::Exception and greatly diminishes the ergonomics of PHP 8.6’s new polling API and stream error handling logic.

PHP Version

PHP 8.6.0-dev (cli) (built: Sep 24 2026 09:04:46) (NTS)
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