Processing more than one task simultaneously saves a lot of time, but a lot of challenge and complexity comes along with this approach. This talk will clarify the differences between fork and thread, when and why to use one or both, their challenges and tricks that save a lot of development time.

1. Cutting Back Processing Time
Executing multiple things at the same time

2. Meet Ed

3. PHP was not made for it, Moody.

4. A lot happen since 1995, Ed.

5. There are better options rather than use PHP
for that, Moody.

6. There can be, and that does not mean that
we should ignore it, Ed.

7. Bla, bla, bla, Moody.

8. Bla, bla, bla, Ed.

9. I don’t like to use PHP for that, Moody.

10. Screw you, Ed.

11. Screw you, Ed.
PHP supports it, we just need to know what
we’re doing.

12. Concurrency & Parallelism

13. Concurrency

14. Parallelism

15. Thread, Process & Fork

16. Thread
• Is the smallest sequence of programmed instructions
• May also be called as “task”
• When in the same process they share resources such as memory

17. Process
• The operating system keeps its processes separate and allocates the
resources they need
• Every process has an ID, a parent, an owner, and a session
• Contains state of all threads executing in a program
• Process may be made up of multiple threads of execution that
execute instructions concurrently

18. One Process, Multiple Threads

19. Multiple Processes & Multiple Threads

20. Fork
• When a process creates a copy of itself

21. Implementing in PHP

22. pthreads
• Implementation of POSIX Threads in PHP
• Works on Unix-like and Windows
• Requires PHP with ZTS (Zend Thread Safety) enabled (--enable-
maintainer-zts or --enable-zts on Windows)
• First stable version in 2014

23. pthreads
final class WorkerThreads extends Thread
{
private $workerId;
public function __construct(int $workerId)
{
$this->workerId = $workerId;
}
public function run()
{
sleep(rand(0, 1));
echo sprintf('Worker "%s" ran', $this->workerId).PHP_EOL;
}
}

24. pthreads
for ($index = 1; $index <= 5; ++$index) {
$worker = new WorkerThreads($index);
$worker->start();
}
echo 'Lekker threads!';

25. pthreads
$ php pthreads.php
Worker "5" ran
Worker "1" ran
Worker "0" ran
Worker "4" ran
Worker "2" ran
Lekker threads!
Worker "3" ran

26. pthreads
final class WorkerPool extends Pool
{
public function wait(): void
{
foreach ($this->workers as $worker) {
$worker->join();
}
}
}

27. pthreads
$pool = new WorkerPool(5);
for ($index = 1; $index <= 5; ++$index) {
$pool->submit(new WorkerThreads($index));
}
$pool->wait();
echo 'Lekker threads!';

28. pthreads
$ php pthreads.php
Worker "5" ran
Worker "1" ran
Worker "0" ran
Worker "2" ran
Worker "4" ran
Worker "3" ran
Lekker threads!

29. PCNTL
• Available since PHP 4
• Works only on Unix-like platforms
• Creation, program execution, signal handling and process
termination
• Does not work on web servers

30. PCNTL
$pid = pcntl_fork();
if ($pid == -1) {
error_log('You have failed this fork...');
exit(1);
}
if ($pid > 0) {
echo sprintf(
'I am the Parent Process and my PID is %d. My child's PID is %d’.PHP_EOL,
getmypid(),
$pid
);
exit();
}
echo 'I am the Child Process and my PID is '.getmypid()." xf0x9fx91xb6";

31. PCNTL
$ php fork.php
I am the Parent Process and my PID is 45179. My child's PID is 45180
I am the Child Process and my PID is 45180 👶

32. POSIX
• Available since PHP 4
• Enabled by default the PHP is compiled
• Interface for POSIX (Portable Operating System Interface) functions
• Works only on Unix-like systems
• Manage process, sessions, groups, users and files

33. POSIX
$uid = 501;
if (posix_setuid($uid) === false) {
error_log(posix_strerror(posix_get_last_error()));
exit(3);
}
$gid = 20;
if (posix_setgid($gid) === false) {
error_log(posix_strerror(posix_get_last_error()));
exit(4);
}
echo 'My PID is '.getmypid().', my UID is '.posix_geteuid().', my GID is '.posix_getgid();

34. POSIX
$ php fork+posix.php
I am the Parent Process and my PID is 45271. My child's PID is 45272
My PID is 45272, my UID is 501, my GID is 20

35. Inter-Process Communication

36. Options for IPC
• Files
• Signals (pcntl_signal(), pcntl_signal_dispatch(), posix_kill(), etc)
• Semaphores (sem_*, load balanced messages)
• Shared Memory (shm_*)
• Message Queue
• Sockets
• DBMS

37. Tricks

38. Forks share nothing
• Ensure yours new-born process can write and read files with umask(0)
• Do not use the same connections
• Replace file descriptors (STDIN, STDOUT and STDERR) or ensure you
don’t write/read them
• Use a lot of logs
• Replace the working directory with something you know that exists, like
chdir(__DIR__)

39. Daemons are independent
• Fork off and die
• Use the init session by calling posix_setsid()
• Save the PID somewhere

40. About Forks
• They are single core
• PHP is not multi-threaded by default
• Forks will be created in the same CPU of its parents
• Easy to overload a server

41. About Threads
• The memory_limit will be respected
• Does not make sense to use on a single core

42. Conclusion

43. Henrique Moody
Software developer focused on PHP.
Addicted to code, patterns, and
development methodologies. Open Source
enthusiast, publisher and contributor of
many projects, and core developer of the
Respect components. Brazilian based in
the Amsterdam working for Werkspot.
@henriquemoody
@henriquemoody

44. References
http://man7.org/linux/man-pages/man7/signal.7.html;
http://www.win.tue.nl/~aeb/linux/lk/lk-10.html;
https://en.wikipedia.org/wiki/Concurrency_(computer_science);
https://en.wikipedia.org/wiki/Cron;
https://en.wikipedia.org/wiki/Daemon_(computing);
https://en.wikipedia.org/wiki/Init;
https://en.wikipedia.org/wiki/Parallel_computing;
https://en.wikipedia.org/wiki/POSIX; https://secure.php.net/ChangeLog-
4.php; https://secure.php.net/cli; https://secure.php.net/ncurses;
https://secure.php.net/newt; https://secure.php.net/pcntl;
https://secure.php.net/posix; https://secure.php.net/pthreads;
https://secure.php.net/readline; https://secure.php.net/readline;
https://secure.php.net/sem; https://www.slideshare.net/jkeppens/php-in-