From ReactPHP to Facebook Hack's Async implementation and many more, asynchronous programming has been a 'hot' topic lately. But how well does async programming support work in PHP and what can you actually use it for in your projects ? Let's look at some real-world use cases and how they leverage the power of async to do things you didn't know PHP could do.

1. The promise of asynchronous PHP
Wim Godden
Cu.be Solutions
@wimgtr

2. Who am I ?
Wim Godden (@wimgtr)

3. Where I'm from

4. Where I'm from

5. Where I'm from

6. Where I'm from

7. Where I'm from

8. Where I'm from

9. My town

10. My town

11. Belgium – the traffic

12. Who am I ?
Wim Godden (@wimgtr)
Founder of Cu.be Solutions (http://cu.be)
Open Source developer since 1997
Developer of OpenX, PHPCompatibility, PHPConsistent, ...
Speaker at Open Source conferences

13. Who are you ?
Developers ?
Ever worked with asynchronous PHP libraries ?
Node.JS ?

14. Synchronous processing

15. Asynchronous processing

16. Blocking I/O
Disk reading/writing
Network reading/writing
Communication with DB (with some exceptions)
Sending mail
...

17. Non-blocking = good
Work on multiple things at same time
Not entirely sequential anymore
How do you know something is finished ?
→ Events !

18. Events
Start
Progress update
End (successfully)
Failed

19. Callback hell
$one->do(function ($two) {
$two->do(function ($three) {
$three->do(function ($stillcounting) {
$stillcounting->get(function() {
throw new IQuitException();
});
});
});
});

20. State of asynchronous PHP
Several built-in functions
Several libraries (using the built-in functions)
Facebook Hack

21. Pthreads
PECL extension
Multithreading
Requires zts (thread-safe)

22. Pthreads
class WebRequest extends Thread {
public $url;
public $response;
public function __construct($url){
$this->url = $url;
}
public function run() {
$this->response = file_get_contents($this->url);
}
}
$request = new WebRequest("http://cu.be");
if ($request->start()) {
/* do some work here */
$a = array_fill(0, 10000000, 'test');
for ($i = 0; $i < count($a); $i++) {}
/* ensure we have data */
$request->join();
var_dump($request->response);
}

23. pcntl_fork
Clones PHP process
Multiprocessing, not multithreading
No communication between processes
No Apache

24. popen
child.php
<?php
/* Do some work */
echo 'Output here';
main.php
<?php
// open child process
$child = popen('php child.php', 'r');
/*
* Do some work, while already doing other
* work in the child process.
*/
// get response from child (if any) as soon at it's ready:
$response = stream_get_contents($child);
W
arning
: doesn't behave
sam
e
on
all operating
system
s
!

25. curl_multi_select
$ch1 = curl_init();
$ch2 = curl_init();
curl_setopt($ch1, CURLOPT_URL, "http://www.google.com/");
curl_setopt($ch2, CURLOPT_URL, "http://www.yahoo.com/");
$mh = curl_multi_init();
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);
$active = null;
do {
do {
$mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
usleep(1000);
} while (curl_multi_select($mh) === -1);
while ($active && $mrc == CURLM_OK) {
if (curl_multi_select($mh) != -1) {
do {
$mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
}
}
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);

26. Libevent, libev, libuv
Event handling libraries
PHP extensions
libevent = also used by Memcached
libev = not available on Windows

27. Using Curl as async system
$c = curl_init();
curl_setopt($c, CURLOPT_URL, 'http://www.long.process.com/calling-
here?action=go&from=4&to=40000');
curl_setopt($c, CURLOPT_FOLLOW_LOCATION, true);
curl_setopt($c, CURLOPT_FRESH_CONNECT, true);
curl_setopt($c, CURLOPT_TIMEOUT_MS, 1);
curl_exec($c);
curl_close($c);
// Code continues after 1ms timeout

28. ReactPHP
Event-driven non-blocking I/O library
Written in PHP
Provides event-driven interface
Implements event loop

29. ReactPHP – a simple webserver
$loop = new ReactEventLoopFactory::create();
$socket = new ReactSocketServer($loop);
$http = new ReactHttpServer($socket, $loop);
$http->on('request', function ($request, $response) {
$response->writeHead(200);
$response->end("Hello world!n");
});
$socket->listen(80);
$loop->run();

30. ReactPHP - structure
Event Loop
Stream
Socket
HTTP
→ stream_select() / libevent / libev

31. ReactPHP - structure
Event Loop
Stream
Socket
HTTPClient DNSWHOIS HTTPClient
WebsocketSOCKS IRC

32. ReactPHP – Deferred & Promise
Computation to be performed = Deferred
(ReactPromiseDeferred)
2 possible status :
Resolved
Rejected

33. ReactPHP – Deferred & Promise
$deferred = new ReactPromiseDeferred();
$promise = $deferred->promise()
->then(
function ($value) {
// Resolved, use $value
},
function ($reason) {
// Rejected, show or log $reason
},
function ($status) {
// Progress changed, show or log $status
}
);

34. ReactPHP – Promises example

35. Hostname lookup – the old way
$hostnames = explode(',', $_POST['hostnames']);
$hostnames = FilterDangerousHostnames($hostnames);
$success = array();
foreach ($hostnames as $hostname) {
$ip = gethostbyname($hostname);
if ($ip != $hostname) {
$success[] = “$hostname ($ip)”;
}
}
echo 'Success resolving ' . implode(', ', $success);
Sequential
→ 10 hostnames → 10 sequential lookups
DNS timeouts → delays

36. Hostname lookup – the async way
$loop = ReactEventLoopFactory::create();
$factory = new ReactDnsResolverFactory();
$dns = $factory->create('8.8.8.8', $loop);
$hostnames = explode(',', $_POST['hostnames']);
$hostnames = FilterDangerousHostnames($_POST['hostnames']);
$promises = array();
foreach ($hostnames as $hostname) {
$promises[] = $dns->resolve($hostname)
->then(
function($ip) use ($hostname) {
return "$hostname ($ip)";
},
function($error) { return ''; }
);
}
ReactPromiseall($promises)->then(
function($hostnames) {
$hostnames = array_filter($hostnames, 'strlen');
echo 'Success in resolving ' . implode(', ', $hostnames) . "n";
}
);
$loop->run();

37. ReactPHP – Chaining then() statements
$promise = $deferred->promise()
->then(
function ($a) {
return $a * 2;
}
)
->then(
function ($b) {
return $b * 2;
}
)
->then(
function ($c) {
echo 'c is now ' . $c;
}
);
$deferred->resolve(1); // Will output 'c is now 4'

38. ReactPHP – Chaining then() statements
$promise = $deferred->promise()
->then(
function ($a) {
if ($a > 5) {
return $a;
} else {
throw new Exception('Too small');
}
}
)
->then(
null,
function ($e) {
echo "We got this exception : " . $e->getMessage();
}
);
$deferred->resolve(10); // Will output nothing
$deferred->resolve(1); // Will output : We got this exception : Too small

39. ReactPHP – Promises vs Streams
Promises
→ Very useful
→ But : limited to simple return values
Streams
→ Much more powerful
→ Also somewhat more complex

40. ReactPHP - Streams
Either :
Readable
Writable
Both
Example :
Through stream = filter
Limited only by your imagination !
$loop = ReactEventLoopFactory::create();
$source = new ReactStreamStream(fopen('source.txt', 'r'), $loop);
$filter = new MyLibStreamAlnumFilter();
$dest = new ReactStreamStream(fopen('dest.txt', 'w'), $loop);
$source->pipe($filter)->pipe($dest);
$loop->run();

41. $loop = ReactEventLoopFactory::create();
$socket = new ReactSocketServer($loop);
$clients = new SplObjectStorage();
$i = 0;
$socket->on('connection', function($connection) use($clients, &$i) {
$connection->id = ++$i;
$connection->write('Enter your nickname: ');
$connection->on('data', function($message) use($clients, $connection) {
if (empty($connection->nickName)) {
$connection->nickName = $message;
} else {
foreach ($clients as $client) {
if ($client->id == $connection->id) {
continue;
}
$client->write(
sprintf(
'<%s> %s',
$connection->nickName,
$message
)
);
}
}
});
$clients->attach($connection);
});
$socket->listen(1337);
$loop->run();

42. Some golden rules & warnings
Golden rule #1 : asynchronous != faster code
Golden rule #2 : don't assume your code will remain as fast
Golden rule #3 : if you don't need a response, don't wait for one
Warning : async does not guarantee execution order !

43. Questions ?

44. Questions ?

45. Thanks !
@wimgtr
wim@cu.be
Please provide some feedback : http://joind.in/13259