The document summarizes HHVM, a virtual machine for executing PHP code. Some key points: - HHVM is a drop-in replacement for PHP that compiles PHP to bytecode and uses a just-in-time (JIT) compiler to optimize for performance. - It supports most PHP syntax and features like Hack which adds type hints. It also has its own features like async functions, user attributes, and XHP for building components with XHTML syntax. - HHVM is faster than PHP due to its JIT compiler which performs type inference and compiles hot code paths to native machine code. Benchmark tests show significant performance improvements over PHP for applications like Magento and Symfony.

1. Hacking with HHVM
Sara Golemon
pollita@php.net
Mar 5, 2014

2. 1 A quick recap
2 PHP is WebScale
3 Sure it’s fast but…
4 Extending HHVM
5 Conclusion / Resources
Agenda

3. A quick recap
“What is HHVM?”

4. HHVM is not a source code transformer
That was HPHPc, it’s dead.
▪ Runs your PHP pages live,
just like PHP
▪ Uses a builtin web server
or FastCGI – Runs anywhere
(on 64-bit x86 linux)
▪ Drop-in replacement for PHP
(mostly)
Webserver
(apache, nginx, etc…)
Database
(mysql, posges,
mongo, redis, etc…)
cart.php
home.phplogin.php
index.php
PHP
A
P
C

5. HHVM is not a source code transformer
That was HPHPc, it’s dead.
▪ Runs your PHP pages live,
just like PHP
▪ Uses a builtin web server
or FastCGI – Runs anywhere
(on 64-bit x86 linux)
▪ Drop-in replacement for PHP
(mostly)
Webserver
(apache, nginx, etc…)
Database
(mysql, posges,
mongo, redis, etc…)
cart.php
home.phplogin.php
index.php
HHVM

6. HHVM supports (most) PHP syntax
Tracking HEAD
▪ Pending: Splat (5.6)
(Variadics work already)
And some of its own
▪ Scalar type hint
(and much much more)
▪ Async co-routines
▪ Generics
▪ Collections (smart arrays)
▪ XHP (Integrated XHTML)
▪ User Attributes

7. HHVM is easy to install
If you’re on Ubuntu
▪ deb http://dl.hhvm.com/ubuntu saucy main
▪ apt-get update
▪ apt-get install hhvm (or hhvm-nightly)
▪ Provides one binary covering cli, fcgi server, and libevent server
▪ Coming very soon to a Debian near you!
Or something Debianish…

8. HHVM is buildable
On other linux distros (MacOSX in interp mode only)
• http://hhvm.com/repo/wiki
• gcc 4.8 or later (soon to be 4.8 or later)
• Boost 1.49 or later
• Lots of other dependencies….
• git clone git@github.com:facebook/hhvm
cmake .
make –j
• hphp/hhvm/hhvm
xkcd.org/303

9. Running a server
Built-in HTTP server FastCGI
Server {
Port = 80
Type = libevent
SourceRoot = /var/www
}
Log {
Level = Error
UseLogFile = true
File = /var/log/hhvm-error.log
Access { * {
File = /var/log/hhvm-access.log
Format = %h %l %u %t ”%r” %>s %b
}}
}
VirtualHost {
…}
StaticFile {
…}
Server {
Port = 9000
Type = fastcgi
SourceRoot = /var/www
}
Log {
Level = Error
UseLogFile = true
File = /var/log/hhvm-error.log
Access { * {
File = /var/log/hhvm-access.log
Format = %h %l %u %t ”%r” %>s %b
}}
}
Requires patched libevent

10. Running a FastCGI server
nginx HHVM
server {
server_name www.example.com;
root /var/www;
index index.php;
location ~ .php$ {
fastcgi_pass unix:/var/run/hhvm.sock
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME
/var/www$fastcgi_script_name;
include fastcgi_param;
}
}
Server {
FileSocket = /var/run/hhvm.sock
Type = fastcgi
SourceRoot = /var/www
}
Log {
Level = Error
UseLogFile = true
File = /var/log/hhvm-error.log
Access { * {
File = /var/log/hhvm-access.log
Format = %h %l %u %t ”%r” %>s %b
}}
}

11. PHP is webscale
HHVM’s JIT is the secret sauce

12. HHVM – Bytecode interpreter
• PHP5 style bytecode execution
• APC-like caching of bytecodes
• Perf about on par with PHP
Modified?
Invalidate
Cache
Compile to
Bytecode
Run
Bytecode
Y
N

13. HHVM – Native code JIT
• Bytecodes run a few times “cold”
• Variable type inference
• Hotpath detection
• Transform to native code
Modified?
Invalidate
Cache
Compile to
Bytecode
Have native?
Run Native
Hot?
Run
Bytecode
Compile to
Native
Y
Y
Y
N
N
N

14. HHVM – Repo Authoritative Mode
• “Production Mode”
• Improved offline pre-analysis
• Assumes no changes
• Another 10% or so perf gain
PreCompil
e Bytecode
Have native?
Run Native
Hot?
Run
Bytecode
Compile to
Native
Y
Y
N
N

15. But don’t take my word for it…

16. Magento (Daniel Sloof)
https://t.co/UB1aOzJ73c

17. Magento (Daniel Sloof)
https://t.co/UB1aOzJ73c

18. Symfony
(Christian Stocker)
Requests per Second
http://bit.ly/1fCRw99

19. Symfony
(Christian Stocker)
Page load Time
http://bit.ly/1fCRw99

20. I heard PHP is getting a JIT…
▪ phpng
▪ Translates Zend bytecode to LLVM intermediate
▪ Compiles to machine code which gets run directly
▪ Yes, it’s faster than PHP 5.6, but not faster than HHVM
▪ LLVM is a general purpose JIT. HHVM was designed for PHP’s “quirks”
▪ HHVM’s variable types were laid out with JITting in mind,
PHP is stuck with the zval
▪ ZE must use a caller frame. HHVM issues direct CPU fcalls
▪ HHVM has access to Hack type hinting/inference

21. Sure it’s fast
But what else can it do?

22. HACK (yes, it’s a horrible name…)
Type Hinting gone mad
▪ Scalars
▪ bool, int, float, num, string
▪ Return typehints
▪ Typed properties
▪ Constructor arg promotion
▪ Specialization
▪ array<int>
▪ array<string,array<string,stdClass>>
Static Analysis
▪ Analyze entire code tree
without running
▪ Report type errors like a
strictly typed language
▪ Fallback on loose typing
when needed
(because that’s what PHP is good at)

23. HACK
<?hh
class Foo {
private int $num = 123;
public function add(int $delta): Foo {
$this->num += $delta;
return $this;
}
public function get(): int {
return $this->num;
}
public function __constructor(int $num): void {
$this->num = $num;
}
}
$f = new Foo(123);
$f->add(456);
$f->add(“banana”);
Basic Hack
▪ Static Analyzer traces value
through whole program
▪ Looks for mismatches and
reports errors
▪ “Foo::add() expected int”
“Foo::add() received string”

24. HACK – Constructor arg promotion
<?hh
class Foo {
public function add(int $delta): Foo {
$this->num += $delta;
return $this;
}
public function get(): int {
return $this->num;
}
public function __constructor(
private int $num) :
void { }
}
$f = new Foo(123);
echo $f->add(456)->get();
Avoid repeated patterns
▪ public/protected/private
as __construct arg modifiers
▪ Declares the property
and initializes from value
▪ Less boilerplate,
more coding

25. HACK – Generics
<?hh
class Foo<T> {
public function add(T $delta): Foo {
$this->num += $delta;
return $this;
}
public function get(): T {
return $this->num;
}
public function __constructor(
private T $num) : void
{ }
}
$i = new Foo<int>(123);
echo $i->add(456)->get();
$f = new Foo<float>(3.14);
echo $f->add(2.17)->get();
Specialize common code
▪ T is replaced w/ specialization
type at instantiation
▪ Typecheker propagates
replacement through generic
▪ Less boilerplate,
more coding

26. HACK – Collections
<?hh
function foo(Vector<int> $nums,
Set<string> $names,
Map<int,string> $numNameMap,
FrozenVector<int> $nums2):
bool {
foreach($nums as $num) {
$mappedName = $numNameMap[$num];
if ($names->contains($mappedName)) {
return true;
}
}
if ($nums2->count() == 0) return true;
return false;
}
Specialized array objects
▪ Vector, Set, Map, StableMap
▪ Frozen*
Mutable* (default)
▪ Support ArrayAccess
▪ Extensive library of methods

27. Async Functions
<?php
// NOT ACTUAL SYNTAX
// Way over-simplified to fit on a slide 
async function getPage($url) {
$fp = fopen($url, ‘r’);
await $fp;
return stream_get_contents($fp);
}
$pages = await [
getPage(‘http://php.net’),
getPage(‘http://example.com’),
getPage(‘http://hhvm.com’),
];
Cooperative Multitasking
▪ Parallelizing made easy
▪ Allow multiple functions to run
“simultaneously”
▪ While one is blocking, the other
executes

28. User Attributes
<?php
<<Author(“sgolemon”),Clowny>>
function life() {
return 42;
}
$rf = new ReflectionFunction(‘life’);
print_r($rf->getAttributes());
print_r($rf->getAttribute(‘Author’));
Array (
[Author] => Array (
[0] => sgolemon
)
[Clowny] => Array ( )
)
Array (
[0] => sgolemon
)
User-defined metadata
▪ Arbitrary labels surfaced via
reflection
▪ Basically what it says on the tin

29. XHP – XHtml for PHP
<?php
if (validate($_GET[‘id’], $_GET[‘pwd’]))
loginAndRedirectToHome();
exit;
}
?><html>
<head><title>Login</title></head>
<body>
<form>
ID: <input type=text name=“username”
value=“{$_GET[‘id’]}” />
Pass: <input type=password name=“password”
value=“{$_GET[‘pwd’]}” />
</form>
</body>
</html>
 Easy noob mistake
▪ http://example.com/?id=“>
<script>alert(“Gotcha!”)</script
>
▪ Trivial vector for stealing user’s
cookies (and login credentials)

30. XHP – XHtml for PHP
<?php
if (validate($_GET[‘id’], $_GET[‘pwd’]))
loginAndRedirectToHome();
exit;
}
include ‘xhp/init.php’;
$form = <form>
ID: <input type=text name=“username”
value=“{$_GET[‘id’]}” />
Pass: <input type=password name=“password”
value=“{$_GET[‘pwd’]}” />
</form>;
echo <html>
<head><title>Login</title></head>
<body>{$form}</body>
</html>;
Markup as 1st
class syntax
▪ Parser can tell what’s userdata,
and what isn’t
▪ Catch most XSS automatically
▪ Formalizes component
modularity

31. XHP – XHtml for PHP
<?php
class :mysite:footer extends :xhp:html-element {
attribute enum {‘en’,’es’} lang = ‘en’;
attribute string prefix;
public function stringify() {
$home = ($this->lang == ‘es’) ? ‘Casa’ : ‘Home’;
$footer = <div class=“footer”>
<a href=“{$this-
>prefix}/”>$home</a>
<a href=“{$this-
>prefix}/contact.php”>
Contact Us
</a>
etc…
</div>;
return (string)$footer;
}
}
echo <html>
<body>
Blah Blah
<mysite:footer lang=‘es’ />
</body>
</html>;
Markup as 1st
class syntax
▪ Custom components
▪ Compose from other tags
or generate custom xhtml

32. XHP – XHtml for PHP
<?php
class :blink extends :xhp:html-element {
category %flow, %phrase;
children (pcdata | %phrase);
protected $tagName = ‘blink’;
}
echo <html>
<body>
<blink>UNDER CONSTRUCTION</blink>
<mysite:footer lang=‘es’ />
</body>
</html>;
Markup as 1st
class syntax
▪ Can also contain other tags
▪ Default :xhp:html-element
behavior makes simple tags easy
▪ Replace :blink’s stringify to use
javascript since browsers disable

33. HPHPd – HPHP Debugger
• Interactive shell
• GDB-like debugging
• Standalone or w/ server
• Breakpoints
• Watches
• Macros

34. Extending HHVM
You *can* do that in PHP

35. Writing a PHP Extension…
zend_bool array_column_param_helper(zval **param,
const char *name TSRMLS_DC) {
switch (Z_TYPE_PP(param)) {
case IS_DOUBLE: convert_to_long_ex(param);
case IS_LONG: return 1;
case IS_OBJECT: convert_to_string_ex(param);
case IS_STRING: return 1;
default: php_error_docref(NULL TSRMLS_CC, E_WARNING, "The %s key should be either a string or an integer", name);
return 0;
}
}
PHP_FUNCTION(array_column) {
zval **zcolumn = NULL, **zkey = NULL, **data;
HashTable *arr_hash;
HashPosition pointer;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "hZ!|Z!", &arr_hash, &zcolumn, &zkey) == FAILURE) { return; }
if ((zcolumn && !array_column_param_helper(zcolumn, "column" TSRMLS_CC)) ||
(zkey && !array_column_param_helper(zkey, "index" TSRMLS_CC))) {
RETURN_FALSE;
}
array_init(return_value);
for (zend_hash_internal_pointer_reset_ex(arr_hash, &pointer);
zend_hash_get_current_data_ex(arr_hash, (void**)&data, &pointer) == SUCCESS;
zend_hash_move_forward_ex(arr_hash, &pointer)) {
zval **zcolval, **zkeyval = NULL;
HashTable *ht;
if (Z_TYPE_PP(data) != IS_ARRAY) { continue; }
ht = Z_ARRVAL_PP(data);
if (!zcolumn) { zcolval = data; }
else if ((Z_TYPE_PP(zcolumn) == IS_STRING) &&
(zend_hash_find(ht, Z_STRVAL_PP(zcolumn), Z_STRLEN_PP(zcolumn) + 1, (void**)&zcolval) == FAILURE)) { continue; }
else if ((Z_TYPE_PP(zcolumn) == IS_LONG) &&
(zend_hash_index_find(ht, Z_LVAL_PP(zcolumn), (void**)&zcolval) == FAILURE)) { continue; }
if (zkey && (Z_TYPE_PP(zkey) == IS_STRING)) { zend_hash_find(ht, Z_STRVAL_PP(zkey), Z_STRLEN_PP(zkey) + 1, (void**)&zkeyval); }
else if (zkey && (Z_TYPE_PP(zkey) == IS_LONG)) { zend_hash_index_find(ht, Z_LVAL_PP(zkey), (void**)&zkeyval); }
Z_ADDREF_PP(zcolval);
if (zkeyval && Z_TYPE_PP(zkeyval) == IS_STRING) { add_assoc_zval(return_value, Z_STRVAL_PP(zkeyval), *zcolval); }
else if (zkeyval && Z_TYPE_PP(zkeyval) == IS_LONG) { add_index_zval(return_value, Z_LVAL_PP(zkeyval), *zcolval); }
else if (zkeyval && Z_TYPE_PP(zkeyval) == IS_OBJECT) {
SEPARATE_ZVAL(zkeyval);
convert_to_string(*zkeyval);
add_assoc_zval(return_value, Z_STRVAL_PP(zkeyval), *zcolval);
} else {
add_next_index_zval(return_value, *zcolval);
}
}
}

36. The same function in HHVM
<?php
function array_column(array $arr, $col, $key = null) {
$ret = [];
foreach($arr as $key => $val) {
if (!is_array($val)) continue;
$cval = ($col === null) ? $val : $val[$col];
if ($key === null || !isset($val[$key])) {
$ret[] = $cval;
} else {
$ret[$val[$key]] = $cval;
}
}
return $ret;
}

37. Crossing the PHP->C++ barrier
Array HHVM_FUNCTION(array_column, CArrRef arr, CVarRef col, CVarRef key) {
Array ret;
for (auto &pair : arr) {
Variant key = pair.first, val = pair.second;
if (val.isArray()) continue;
Array aval = val.toArray();
Variant cval = col.isNull() ? aval : aval[col];
if (key.isNull() || !aval.exists(key)) {
ret.append(cval);
} else {
ret[aval[key]] = cval;
}
}
return ret;
}

38. Blurring the PHP/C++ line
class MyClass {
public static function escapeString(string $str): string {
return str_replace(“’”, “’”, $str);
}
<<__Native>>
public funtion query(string $sql): array;
}
Array HHVM_METHOD(MyClass, query, const String& sql) {
// Call C/C++ library function and return result…
// Called object available as: CObjRef this_
// Static calls come through: Class *self_
}

39. Questions
?

40. Resources
• http://hhvm.com/repo
• http://hhvm.com/blog
• http://hhvm.com/twitter
• http://docs.hhvm.com
• hphp/doc in git repository for Options and Technical… Stuff
• Freenode / #hhvm
• http://hhvm.com/fb/page
• http://hhvm.com/fb/general
• @HipHopVM
• @HackLang