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Changelog - Version 7.0

Status: in development. This document tracks changes landing on the 7.0 branch. Nothing here is released yet, and the contents may still change.

Breaking Changes​

Enum cases renamed to PascalCase​

Enum cases follow the ByJG standard and are written in PascalCase. The backed values of PromiseStatus did not change, so ->value, from(), tryFrom() and stored data are not affected; only code that names a case (or reads ->name) has to be updated. ThreadStatus is a pure (non-backed) enum, so any code that names its cases has to be updated.

EnumBefore (6.x)After (7.0)
PromiseStatuspending, fulfilled, rejectedPending, Fulfilled, Rejected
ThreadStatusnotStarted, running, finished, errorNotStarted, Running, Finished, Error

ForkHandler keeps its state after getResult()​

ForkHandler::getStatus() returns Finished after getResult(), not NotStarted, and a second getResult() returns (or re-throws) the result instead of null (see Bug Fixes).

Promise then/catch/finally follow JavaScript​

  • A rejection handled by then($onFulfilled, $onRejected) or catch($onRejected) now resolves the returned promise with the handler's return value, so the chain continues on the fulfilled path. Before, the returned promise was rejected again with that value: Promise::reject(1)->then(fn($v) => $v + 2, fn($r) => $r + 5)->then(fn($v) => $v + 10, fn($r) => $r + 2) gave 8, it gives 16 now. To keep a promise rejected from a handler, throw an exception in it.
  • finally($onFinally) calls the callback with no argument and ignores its return value; the returned promise settles with the original value or reason. Before, the callback received the value (or reason) and the returned promise resolved with whatever it returned. A callback declared with a required parameter (fn($value) => ...) now fails, since it is called with no argument; declare it without one.

Thread::create() no longer throws outside the CLI​

Thread::create() (and so Promise and ThreadPool) threw a RuntimeException ("Threads only works in CLI mode", or "PHP need to be compiled with ZTS extension or compiled with the --enable-pcntl") under PHP-FPM or any other non-CLI SAPI, or without pcntl_fork() and parallel. It now returns a ProcessHandler, which runs the closure in a child PHP CLI process, or, without proc_open() or a PHP CLI binary, a SyncHandler that runs the closure synchronously (see New Features). Code that caught that exception to detect an unsupported environment should check Thread::handlerClass() instead. ForkHandler and ParallelHandler still throw when instantiated directly outside the CLI.

Promise::all() keeps the order of the promises​

Promise::all() resolves with the results in the order of the promises passed to it, as in JavaScript. Before, they were in the order the promises settled (see Bug Fixes).

A promise whose thread ends without settling it is rejected​

An executor that returns without calling $resolve or $reject now rejects the promise with a RuntimeException ("The thread ended without settling the promise ..."), instead of leaving it pending (see Bug Fixes).

New Features​

Promise::try()​

  • Promise::try(Closure $closure, mixed ...$args) runs the closure in a thread and returns a promise fulfilled with its return value or rejected with what it throws, as Promise.try() in JavaScript. See docs/promises.md.

Promise::map()​

  • Promise::map(iterable $items, Closure $callback, int $concurrency) runs the callback for each item in a thread, at most $concurrency at a time, and resolves with the values in the order of the items (or rejects with the first rejection). Promise::all() starts every promise at once. See docs/promises.md.

A returned promise is followed​

  • A promise returned by a then()/catch() callback or by Promise::try(), or passed to $resolve, is followed as in JavaScript: the promise settles with its value or reason. The thread waits for the inner promise, since a promise cannot be shared between threads. Before, the promise could not be stored in the shared memory and the outer promise ended rejected ("The thread ended without settling the promise"). See docs/promises.md (Returning a promise).

SyncHandler: synchronous fallback​

  • New ByJG\PHPThread\Handler\SyncHandler: runs the closure in the current process when start() is called and keeps its result, or the exception it threw, which getResult() re-throws on every call (as ForkHandler). isRunning() is always false, join() and terminate() do nothing, getStatus() is NotStarted before start() and Finished after it, and $onFinish is called after the closure.
  • Thread::create() picks the handler automatically: ParallelHandler in the CLI with the parallel extension, ForkHandler in the CLI with pcntl_fork(), SyncHandler otherwise. Threads, thread pools and promises therefore work under PHP-FPM, without parallelism.
  • New Thread::handlerClass() returns the handler class Thread::create() uses.
  • New Thread::useHandler(?string $handlerClass) forces the handler Thread::create() uses (ParallelHandler, ForkHandler or SyncHandler; any other class throws InvalidArgumentException), e.g. SyncHandler in tests or for a deterministic run; null restores the automatic choice. A forced ForkHandler or ParallelHandler still throws when it cannot run. The promise and thread pool tests run with both ForkHandler and SyncHandler.

ProcessHandler: parallel threads outside the CLI​

  • New ByJG\PHPThread\Handler\ProcessHandler: runs the closure in a child PHP CLI process started with proc_open() (the approach of amphp/parallel), so threads, thread pools and promises run in parallel under PHP-FPM, FrankenPHP or any other SAPI. The closure, its arguments and $onFinish are serialized with laravel/serializable-closure; the child (src/Handler/process-worker.php) loads the project's Composer autoloader, runs the closure and $onFinish, and sends back the result or the exception, which getResult() re-throws (as ForkHandler). getResult() waits for the child. terminate() uses proc_terminate().
  • The closure, its arguments, what it captures and its result must be serializable (no resources), the child does not run the application bootstrap, and two closures on the same line can be mixed up by the serializer. See docs/thread.md (ProcessHandler) and docs/limitations.md.
  • ProcessHandler::setPhpBinary(?string) sets the PHP CLI binary (default: PHP_BINARY in the CLI, otherwise PHP_BINDIR/php or php in the PATH); getPhpBinary() and isAvailable() tell what is used.
  • Thread::create() picks the ProcessHandler when ParallelHandler and ForkHandler cannot be used (outside the CLI, or a CLI without parallel/pcntl) and proc_open() and a PHP CLI binary are available; the SyncHandler is now the last fallback. Thread::useHandler() accepts ProcessHandler::class.
  • SharedMemory::getPrefix() and SharedMemory::usePrefix() (@internal) let the child process share the parent's shared memory (used by the promises).
  • The promise and thread pool tests also run with the ProcessHandler.

Bug Fixes​

  • then() with an $onRejected handler and catch() rejected the returned promise with the handler's return value instead of resolving it, so a handled rejection could not be recovered from; and finally() replaced the promise's value or reason with the callback's return value, and turned a rejected promise into a fulfilled one. Both now follow the JavaScript Promise semantics (see Breaking Changes). A handler or finally callback that throws rejects the returned promise with that exception.

  • ForkHandler::getResult() cleared the thread key, so the thread looked as if it had never been started: getStatus() returned NotStarted and every later getResult() returned null. The result is now read from the shared memory once and kept; start() clears it for the next run.

  • A PHP Error (TypeError, ArgumentCountError, a call on a non-object, ...) thrown by an executor or a callback was not caught, so the promise never settled: await() threw "Promise result is null" and anything chained after it never returned. It now rejects the promise, like an exception. A finally() callback still written as fn($value) => ... gets no argument and rejects with ArgumentCountError.

  • Promise::all() resolved with the results in the order the promises settled, not the order they were passed in, so Promise::all($slow, $fast) gave [fast, slow] with the ForkHandler. The results now follow the order of the promises, as in JavaScript.

  • A promise whose thread died (fatal error, exit, killed) or whose executor returned without settling it stayed pending forever: await() threw "Promise result is null" and the promises chained to it (then, catch, finally, all, race), which wait in other processes, never returned. The process that created the promise now rejects it with a RuntimeException (the ProcessHandler gives the exit code) and shares the rejection with the chained promises, which reject with the same reason.

Requirements​

  • ext-pcntl and ext-posix moved from require to suggest: they are only needed by the ForkHandler, which checks that both are loaded (ForkHandler::isAvailable()). Without them Thread::create() uses the ProcessHandler in the CLI too. src/polyfill.php (Composer files autoload) defines SIGKILL and SIGTERM when pcntl is not loaded.

  • New dependency laravel/serializable-closure ^2.1 (requires php ^8.1), used by the ProcessHandler to send the closures to the child process.

  • PHP 8.3, 8.4, 8.5 and 8.6 are now supported: "php": ">=8.3 <8.7". The previous <8.6 upper bound excluded PHP 8.6, since <8.6 is exclusive.

ByJG dependencies​

  • byjg/cache-engine is now ^7.0.
  • byjg/restserver is now ^7.0.

While 7.0 is unreleased these resolve to 7.0.x-dev from each component's 7.0 branch, via minimum-stability: dev with prefer-stable: true.

Toolchain​

  • PHPUnit updated to ^12.5.

  • Psalm is installed as psalm/phar instead of vimeo/psalm.

    vimeo/psalm lists the PHP versions it supports and no published release includes 8.6, so as a dev dependency it made composer install fail on the 8.6 build job before any test ran. psalm/phar requires only php ^8.2 and bundles its own dependencies, so it installs on every PHP version in the matrix and cannot conflict with the project's. Psalm itself still refuses to run on 8.6, which is why the Psalm job uses 8.5. composer psalm runs it.

  • PHPUnit 13 is deliberately not used. It requires PHP >=8.4.1, breaking the 8.3 floor.

Continuous Integration​

  • The build matrix now includes PHP 8.6.
  • The Psalm job runs on PHP 8.5.
  • The PHP-FPM check expects the /thread, /threadpool and /promise endpoints to return their results (computed by the ProcessHandler, in parallel) instead of the "Threads only works in CLI mode" error, and the new /handler endpoint to report the ProcessHandler.

Housekeeping​

  • The test suite runs faster: the sleeps are tenths of a second instead of seconds, and the timing-dependent scenarios (race order, parallelism) run only with the parallel handlers. PHPUnit enforces a 20 s limit per test (enforceTimeLimit, failOnRisky), so a test that would hang fails instead.

  • phpunit.xml.dist renamed to phpunit.xml.