A look at Facebook's HipHop for PHP library, both the first generation, HPHPc, and the new HHVM. This presentation walks through the challenges that faced Facebook and their PHP-based solution from a year after their explosive growth in 2007 to late-2013.

1. Steve Kamerman | ScientiaMobile, Inc.
Co-Founder / Software Architect
High-Performance PHP with HipHop

3. 2008 - Facebook's Challenge
●
Explosive growth
●
Need more servers!
●
Bottleneck: Page generation
●
20% of PHP time was in native code

4. Why is PHP so slow?
●
Symbol table lookups
●
No static binding
●
Dynamic typing
●
Share-Nothing-Architecture

5. 2008-2010 – HipHop for PHP is born
●
400 Billion PHP-generated pageviews per
month!
●
Facebook invents HipHop for PHP
●
Deployed system-wide in 2010

6. HipHop for PHP
Research &
Development
HPHPc
HHVM

7. What is HipHop for PHP?
• Multi-threaded web server + PHP runtime
• HPHPc: PHP -> C++ translator
• HHVM: PHP virtual machine with JIT
compiler
• Typically 2x – 5x speed increase over stock
PHP + APC

8. HipHop for PHP Compiler (HPHPc)
●
Translates PHP code into C++
●
Dynamic typing makes this difficult
●
Function parity lacking
●
Long compilation time

9. Our Experience
●
Created WURFL Cloud REST API
●
Evaluated HPHPc
●
Improved Latency
●
Stability issues

10. Architecture
Internet
HAProxy
Load Balancer
(primary)
WURFL Node
HPHPc
Apache
WURFL Node
HPHPc
Apache
HAProxy
Load Balancer
(secondary)
WURFL Node
HPHPc
Apache
WURFL Node
HPHPc
Apache
Memcached
Memcached
Memcached
Memcached
MySQL
MySQL
MySQL
MySQL

11. Codebase Updates
http://www.github.com/kamermans/HAProxyAPI

12. Next-Gen HipHop: HHVM
●
Virtual Machine
●
Better PHP Support
●
JIT Compiler
●
Bytecode Survives Restart

13. How HHVM works
Internet
HHV
M
Web Server
Run Native
Code
Run Bytecode
Generate
Bytecode
JIT Compile

14. HHVM vs HPHPc Performance
http://www.hhvm.com/blog/875/wow-hhvm-is-fast-too-bad-it-doesnt-run-my-code
https://github.com/facebook/hhvm/blob/master/hphp/doc/ir.specification

15. Optimizing PHP for HHVM
●
Type Inference
–
PHP Gotcha: core function fail with (bool)false
●
HHVM Upgrades primitives
●
Use strict comparison

16. Don't care about type strict comparison?
You should. Trust me.
var_export("true" == true); // true
var_export("false" == true); // true
var_export("true" == (bool)"false"); // true
var_export(strpos("Steve Kamerman", "Kamerman") == true); // true
var_export(strpos("Steve Kamerman", "Steve") == true); // false
$test = "31 is too old!";
var_export(31 == $test); // true
var_export("31.0" == 31); // true
var_export("031" == 031); // false
var_export(31.0 == 31); // true
var_export($test += 1); // 32

17. Avoid global scope
●
●
Code in the global scope is interpreted since it
is (nearly) impossible to type-track
Even wrapping global code helps:
class foo{public static function bar(){
$something = "test";
echo $something;
}}foo::bar();
●
Better approach: don’t write crappy code!

18. Unique Classes, Functions, Constants
●
HHVM supports namespaces – use them!
●
MyAppBar and MyAppFooBar are not ambiguous
●
●
●
Avoid “dynamic” constants:
define("MY_CONST", $foo? "foo": "bar");
I can almost picture a feature request for
undefine() and redefine()
If they are truly constant, use const

19. Better approach: don't use define()
namespace MyApp;
class Config {
const MY_CONST = "I'm real constant";
private static $storage = array(
"PSEUDO_CONSTANT" => "What did you call me?",
);
public static function get($name) {
if (!array_key_exists($name, self::$storage)) {
throw new Exception(__CLASS__." property [$name] does
not exist");
}
return self::$storage[$name];
}
}
echo Config::MY_CONST."n";

20. Avoid dynamic variables
●
If you are using this syntax, there is a better way to solve
the problem:
$foo = "Wow, this hurts my brain!";
$var_name = "foo";
echo $$var_name;
●
●
extract() and compact() are sometimes used more
legitimately (ex: view rendering), but avoid them
If you need get_defined_vars() for non-testing code,
you need to rewrite it before someone sees it :)

21. Declare class properties
●
They should be declared anyway
$foo = new stdClass();
echo $foo->bar; // PHP Notice: Undefined
property
●
Getters are optimized

22. Perfomance Gain
●
●
Less than 5%, but still good practice
Sub-optimal functions still work, even
eval() and goto!
http://php.net/manual/en/control-structures.goto.php

23. Repo.Authoritative Mode
●
Pre-Analyze files
●
PHP files assumed unchanged
●
Delete cache manually

24. Current state of HipHop
●
HHVM v2.2.0 just released
●
Very close to PHP 5.4
●
Dozens of extensions
●
Performance nearly 5x
●
Goal: Support top 20 frameworks in 2013

25. Framework Support
Framework % Unit Tests Pass
Framework % Unit Tests Pass
Facebook PHP SDK 100
CodeIgniter 81
Paris9 100
Assetic 80
Idiorm9 100
Twig 78
Slim 99
Wordpress 76
Drupal 98
phpBB 0
Composer 97
CakePHP 0
Laravel 95
Joomla 0
yii 92
PHPMyAdmin 0
Symfony 91
zf2 0
PHPUnit2 90
Doctrine 0
Magento 0
http://www.hhvm.com/blog/875/wow-hhvm-is-fast-too-bad-it-doesnt-run-my-code

26. Why is it open source? Will it last?
●
Under PHP license, hard to separate
●
Public activity slowed in 2011
●
Under active public development in 2012-13
●
Dev team is active on IRC (freenode #hhvm)

27. Facebook's Commitment
“In years past we've had a few examples of projects which have not
been well supported, but we are now much better at growing and
sustaining community projects, including, lately, in mobile.
[HipHop for PHP] is absolutely a project that we stand strongly
behind… stay tuned.”
James Pearce, Head of Developer Advocacy at Facebook

28. References
●
●
●
●
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Special thanks to the HipHop for PHP team!
https://www.facebook.com/hphp
Twitter: @HipHopVM
http://www.hhvm.com/
Sebastian Bergmann – Static Code Analysis with HipHop
http://sebastian-bergmann.de/archives/918-Static-Analysis-with-HipHop-for-PHP.html
http://www.slideshare.net/nickgsuperstar/static-analysis-for-php
https://github.com/sebastianbergmann/hhvm-wrapper
Haiping Zhao – HipHop Compiler for PHP? Transforming PHP into C++
http://www.youtube.com/watch?v=p5S1K60mhQU
Sara Golemon – Scaling with HipHop
http://www.youtube.com/watch?v=Dwek7dZDFN0
Ben Foster – Facebook Growth Data
http://www.benphoster.com/facebook-user-growth-chart-2004-2010/