HHVM is currently gaining popularity at quite a pace, and it's a pretty exciting time for PHP runtimes. Have you ever wondered what is going on beneath this slick and super-speedy engine? I wondered that myself, so I dived into the internals of HHVM, discovering a treasure trove of awesome stuff. In this talk, I’ll show you how HHVM itself works with a guided tour of the codebase, demonstrating how it all pieces together. I’ll also show you a couple of ways to write your own incredible HHVM extension. You don't need to know C++ to understand this talk - just PHP language knowledge is enough.

1. Diving into
HHVM Extensions
James Titcumb
BrnoPHP Conference 2015

2. James Titcumb
www.jamestitcumb.com
www.roave.com
www.phphants.co.uk
www.phpsouthcoast.co.uk
@asgrim
Who is this guy?

3. First, some background...
source: Microsoft

7. How PHP works
PHP code
OpCache
Execute (VM)
Lexer + Parser
Compiler

8. How HHVM works
PHP code
OpCache
Execute (VM)
Lexer + Parser
Compiler
JIT
Execute (Native)

9. Hack features
● Return/parameter type hints
● ?nullable
● Collections (Vectors, Sets, Maps, etc.)
● Async functions
● Enums
● Generics
● Lambda expressions ==>
● XHP
● more stuff

10. The HHVM codebase

11. The Engine
hphp/parser

12. The Engine
hphp/parser
hphp/compiler

13. The Engine
hphp/parser
hphp/compiler
hphp/hhbbc

14. The Engine
hphp/parser
hphp/compiler
hphp/hhbbc
hphp/hhvm

15. The Engine
hphp/parser
hphp/compiler
hphp/hhbbc
hphp/hhvm
hphp/runtime/vm

16. The Engine
hphp/parser
hphp/compiler
hphp/hhbbc
hphp/hhvm
hphp/runtime/vm
hphp/runtime/vm/jit

17. The Extensions
hphp/runtime/ext

18. The Extensions
hphp/runtime/ext
hphp/system/php

19. Compile HHVM?

20. source: https://xkcd.com/303/

21. My First HHVM Extension™

22. config.cmake
HHVM_EXTENSION(calc ext_calc.cpp)

23. ext_calc.cpp
#include "hphp/runtime/ext/extension.h"
namespace HPHP {
static class CalcExtension : public Extension {
public:
CalcExtension(): Extension("calc") {}
virtual void moduleInit() {}
} s_calc_extension;
HHVM_GET_MODULE(calc);
} // namespace HPHP

24. ext_calc.cpp
#include "hphp/runtime/ext/extension.h"
namespace HPHP {
static class CalcExtension : public Extension {
public:
CalcExtension(): Extension("calc") {}
virtual void moduleInit() {}
} s_calc_extension;
HHVM_GET_MODULE(calc);
} // namespace HPHP

25. ext_calc.cpp
#include "hphp/runtime/ext/extension.h"
namespace HPHP {
static class CalcExtension : public Extension {
public:
CalcExtension(): Extension("calc") {}
virtual void moduleInit() {}
} s_calc_extension;
HHVM_GET_MODULE(calc);
} // namespace HPHP

26. ext_calc.cpp
#include "hphp/runtime/ext/extension.h"
namespace HPHP {
static class CalcExtension : public Extension {
public:
CalcExtension(): Extension("calc") {}
virtual void moduleInit() {}
} s_calc_extension;
HHVM_GET_MODULE(calc);
} // namespace HPHP

27. ext_calc.cpp
#include "hphp/runtime/ext/extension.h"
namespace HPHP {
static class CalcExtension : public Extension {
public:
CalcExtension(): Extension("calc") {}
virtual void moduleInit() {}
} s_calc_extension;
HHVM_GET_MODULE(calc);
} // namespace HPHP

28. … that’s it.
<?php
var_dump(extension_loaded('calc'));
test.php

29. Compile it.
(waaaat?!)

30. Compile & run the test
#!/bin/bash
hphpize
cmake . && make
/usr/bin/hhvm
-d extension_dir=.
-d hhvm.extensions[]=calc.so
test.php

31. Compile & run the test
$ ./build.sh
bool(true)
$

32. Hack it!

33. source: http://goo.gl/kUAxBI

34. config.cmake
HHVM_EXTENSION(calc ext_calc.cpp)
HHVM_SYSTEMLIB(calc ext_calc.php)

35. ext_calc.cpp
#include "hphp/runtime/ext/extension.h"
namespace HPHP {
static class CalcExtension : public Extension {
public:
CalcExtension(): Extension("calc") {}
virtual void moduleInit() {
loadSystemlib();
}
} s_calc_extension;
HHVM_GET_MODULE(calc);
} // namespace HPHP

36. ext_calc.php
<?hh
function calc_sub(int $a, int $b): int {
return $a - $b;
}

37. … that’s it.
<?php
var_dump(extension_loaded('calc'));
var_dump(calc_sub(5, 3));
test.php

38. Compile & run the test
$ ./build.sh
bool(true)
int(2)
$

39. Sprinkle some C++ in
for good measure

40. ext_calc.cpp
// ... SNIP ...
virtual void moduleInit() {
HHVM_FE(calc_add);
loadSystemlib();
}
// ... SNIP ...

41. ext_calc.cpp
// ... SNIP ...
static int64_t HHVM_FUNCTION(calc_add, int64_t a, int64_t b) {
return a + b;
}
// ... SNIP ...

42. in php extensions...
PHP_FUNCTION(calc_add)
{
// ... SNIP ...
#ifndef FAST_ZPP
if (zend_parse_parameters(ZEND_NUM_ARGS(), "ll", &a, &b) == FAILURE) {
return;
}
#else
ZEND_PARSE_PARAMETERS_START(2, 2)
Z_PARAM_LONG(a)
Z_PARAM_LONG(b)
ZEND_PARSE_PARAMETERS_END();
#endif
// ... SNIP ...

43. ext_calc.php
<?hh
<<__Native>>
function calc_add(int $a, int $b): int;
function calc_sub(int $a, int $b): int {
return $a - $b;
}

44. … that’s it.
<?php
var_dump(extension_loaded('calc'));
var_dump(calc_sub(5, 3));
var_dump(calc_add(5, 3));
test.php

45. Compile & run the test
$ ./build.sh
bool(true)
int(2)
int(8)
$

46. Debugging?!

47. source: http://www.gnu.org/software/gdb/

48. Add debug mode
#!/bin/bash
hphpize
cmake
-DCMAKE_C_FLAGS="-O0 -ggdb3"
-DCMAKE_CXX_FLAGS="-O0 -ggdb3"
-DCMAKE_BUILD_TYPE=Debug
.
make
# ... SNIP ...

49. Run with gdb
$ gdb --args
/usr/bin/hhvm
-d extension_dir=.
-d hhvm.extensions[]=calc.so
test.php
GNU gdb (Ubuntu 7.9-1ubuntu1) 7.9
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.
org/licenses/gpl.html>
--- snip ---
Reading symbols from /usr/bin/hhvm...done.
(gdb)

50. Breakpoints
(gdb) b ext_calc.cpp:6
No source file named ext_calc.cpp.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (ext_calc.cpp:6) pending.
(gdb)

51. Running
(gdb) r
Starting program: /usr/bin/hhvm -d extension_dir=. -d hhvm.extensions[]
=calc.so smoke.php
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 2, HPHP::f_calc_add (a=5, b=3) at /home/james/workspace/hhvm-
calc/ext_calc.cpp:6
6 return a + b;
(gdb) p a
$1 = 5
(gdb) p b
$2 = 3
(gdb)

52. Handy commands
c continue / step out
n step over
s step into
p x print the value of a variable (x)
set x = y set a variable (x) to value (y)
bt print backtrace
q quit :)

53. When NOT to write extensions

54. When to write extensions

55. BUCKLE UP.

56. source: https://goo.gl/x7Srhe

57. Integrating OpenGL
into an HHVM extension

58. Don’t try this in
production!

59. srsly.

60. Extension
Browser

61. What I did

63. huh?!

64. Make it OOOOOOO

65. ext_foo.php
<?hh
<<__NativeData("Foo")>>
class Foo {
<<__Native>>
public function bar(): int;
}

66. C++ object
!==
PHP object

67. source: http://goo.gl/HORwLQ

68. HHVM Universe
<?php
$o = new Foo();
$o->bar();
PHP Land
class Foo {
public:
Foo() {}
~Foo() {}
int value = 5;
}
Planet C++
int64_t HHVM_METHOD(Foo,bar)
{
auto data =
Native::data<Foo>(this_);
return data->value;
}
Time Vortex!?!?!
C++ object !== PHP object

69. HHVM Universe
<?php
$o = new Foo();
$o->bar();
PHP Land
class Foo {
public:
Foo() {}
~Foo() {}
int value = 5;
}
Planet C++
int64_t HHVM_METHOD(Foo,bar)
{
auto data =
Native::data<Foo>(this_);
return data->value;
}
Time Vortex!?!?!
C++ object !== PHP object

70. HHVM Universe
<?php
$o = new Foo();
$o->bar();
PHP Land
class Foo {
public:
Foo() {}
~Foo() {}
int value = 5;
}
Planet C++
int64_t HHVM_METHOD(Foo,bar)
{
auto data =
Native::data<Foo>(this_);
return data->value;
}
Time Vortex!?!?!
C++ object !== PHP object

71. HHVM Universe
<?php
$o = new Foo();
$o->bar();
PHP Land
class Foo {
public:
Foo() {}
~Foo() {}
int value = 5;
}
Planet C++
int64_t HHVM_METHOD(Foo,bar)
{
auto data =
Native::data<Foo>(this_);
return data->value;
}
Time Vortex!?!?!
C++ object !== PHP object

72. this slide is intentionally left blank

73. ext_foo.php
<?hh
class Foo {
private int $value
public function bar(): int
{
return $this->value;
}
}

74. Demo?

76. source: http://goo.gl/7gWfNz

77. Resources
● OpenGL Tutorial
○ http://www.opengl-tutorial.org/
● HHVM Example Extension
○ https://github.com/hhvm/extension-example
● Sara Golemon - HHVM extension blog series
○ http://blog.golemon.com/2015/01/hhvm-extension-writing-part-iii.html
● Derick Rethans’ extension API cookbook
○ https://github.com/derickr/hhvm-hni-cookbook
● The official API documentation
○ https://github.com/facebook/hhvm/wiki/Extension%20API
● Journey of a Thousand Bytecodes
○ http://hhvm.com/blog/6323/the-journey-of-a-thousand-bytecodes

78. Any questions? :)
https://joind.in/16263
James Titcumb @asgrim