Reactive programming in PHP

Reactive Programming
in PHP
Johney Park
2018.06.17

Reactive Programming
=
Observer Pattern
+ LINQ-style operators
( + Schedulers)
TL; DR

Pros:
Good for handling async events
Cons:
Difficult to understand
Too many things to learn
Some overhead
TL; DR

Definition
Reactive Programming is
programming with
asynchronous
data streams.
https://gist.github.com/
staltz/868e7e9bc2a7b8c1f754
(Where is reactive?)

What you heard when you
learn reactive programming
• Observer/Observable / Hot & Cold
• Signal / Flux / Stream / EventStream / EventSource / …
• Subject
• Scheduler
• Publish / Subscribe / Unsubscribe / Dispose / Behavior
• Producer / Consumer
• Map / Reduce / Throttle / …

Observer Pattern
Observer 1
Observable
watch & run
Observer 2
♨
(Event Source)
wrap

Observer Pattern
Observer 1
Observable
subscribe
Lazy Evaluation
Subscription 1
async call with
stream operators
Observer 2 Subscription 2
Observers don’t observe
Observable does all the work
Producer / Consumer may be better naming

Observer Pattern
Observer 1
Observable 1
Observer 2
Observer 3
Subject 1
Subject 2
Subject = Observable + Observer
broadcast
♨
(Event Source)
♨
(Event Source)
direct call

When to use RP?
• One or more event sources
• Require stream operators
• Not a perfect solution for all
async scenarios
• External API Call (MSA)
• UI Events (Click)
• Message Processing
• Abstraction over Async Process

RxPHP
• stream_select (PHP 4 >= 4.3.0, PHP 5, PHP 7)
• ReactPHP != RxPHP
• ReactPHP is event-driven, non-blocking I/O library
• EventLoop, Promise from ReactPHP
• https://github.com/ReactiveX/RxPHP

RxPHP
$source = RxObservable ::fromArray([1, 2, 3, 4]);
$observer = new RxObserverCallbackObserver(
function ($x) {
echo 'Next: ', $x, PHP_EOL;
},
function (Exception $ex) {
echo 'Error: ', $ex ->getMessage(), PHP_EOL;
},
function () {
echo 'Completed', PHP_EOL;
});
$source ->subscribe($observer);
// Next: 1
// Next: 2
// Next: 3
// Next: 4
// Completed
Very simple sample code
• Cold Observable Sample, almost
useless
• Source = Observable
• Subscribe Observer to
Observable
• Observer is consist of three
functions
• next, error, completed

RxPHP
$loop = Factory ::create();
Scheduler ::setDefaultFactory(function () use ($loop) {
return new SchedulerEventLoopScheduler($loop);
});
register_shutdown_function(function () use ($loop) {
$loop ->run();
});
Observable ::interval(1000)
->take(5)
->flatMap(function ($i) {
return Observable ::of($i + 1);
})
->subscribe(function ($e) {
echo $e, PHP_EOL;
});
// 1
// 2
// 3
// 4
// 5
Event Loop
• We need to set EventLoop when using
stream operator
• interval, throttle, etc..
• If you don’t use stream operator, you
don’t need to set EventLoop
• RxJs don’t require explicit event loop,
because Javascript has setTimeout,
setInterval, requestAnimationFrame
• There are many scheduler types
• flatMap == mergeMap, but RxPHP don’t
provide mergeMap

RxPHP
$subject = new RxSubjectSubject();
$subject ->subscribe(function($i) { echo $i . PHP_EOL;});
RxObservable ::interval(1000)
->take(5)
->flatMap(function ($i) {
return Observable ::of($i + 1);
})
->subscribe($subject);
$subject ->onNext(10);
// 10
// 20
// 30
// 1
// 2
// 3
// 4
// 5
Subject
• Subject = Observable +
Observer
• Actually Subject is extended
from Observable
• You don’t need to create custom
Observable for simple usage

RxPHP
More Samples
• https://github.com/ReactiveX/RxPHP/tree/master/demo
• https://github.com/PacktPublishing/PHP-Reactive-
Programming/
• https://www.packtpub.com/web-development/php-
reactive-programming

RxPHP
Ben Lesh’s comment
RxJS could be so simple... just a handful of types and operators.
... but if we do that, then people shoot themselves in the foot with memory
leaks and their own poorly implemented `expand` operator or whatever… ...
so then we add 60+ operators and people are like "WHOA...." haha.. Now it's
too complicated.
It's tough everywhere. Haha
If I had a nickel for every poorly implemented custom RxJS operator I've
seen… ... I'd only have about 25 cents, because we've already built almost
every tool someone could want.
But who have we scared off in the process?

Reactive programming in PHP

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