PHP, Under The Hood - DPC
PHP is one of the most popular open source programming languages in the world. It powers some of the highest traffic sites in the world, and at the same time it powers some of the lowest traffic sites in the world. But have you ever wondered how it works under the hood? Have you been overwelmed by the thought of looking at the C code that runs PHP? Well, this talk is for you! We're going to explore how PHP works under the hood, by looking at a PHP implementation of it: PHPPHP! Have you ever wondered what an OPCODE Cache is really doing? Have you ever wondered what a T_PAAMAYIM_NEKUDOTAYIM is? Have you ever wondered why an interpreted languages has a compiler? We'll explore all of these topics, and more! And the best part of it all? You don't need to know C to understand the details! Using PHPPHP, we can explore the language details in a high level language, where things like memory management don't get in the way of the real content. If you've ever wanted to know how PHP works, this is the talk for you!
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PHP, Under The Hood - DPC
- 2. What Is PHP? ● An Easy To Learn Language? ○ Sure! ● A Simple Language? ○ Usually ● A Well Designed Language? ○ HA! ● An Effective Language! ○ Absolutely!
- 5. $a = 1; $b = "a";
- 7. 1 + "1b" == 2
- 9. Implementations Main: C-PHP: www.php.net Alt: HipHop - Facebook Roadsend - Compiler Phalanger - .NET PHP Compiler - Compiler PHPPHP - PHP
- 11. Interesting Note: C-PHP Requires PHP To Compile!
- 16. It All Starts With The SAPI
- 17. SAPI ● Server API ● "Starts" PHP and issues request(s) ● Common SAPIs: ○ CLI ○ CGI (and FastCGI) ○ mod_php ○ FPM ○ etc...
- 19. Execution Pipeline Start Up Request Shut Down SAPI
- 20. Execution Pipeline Start Up Request Shut Down SAPI Config Init Engine Init Module Init
- 21. Zend/zend.c
- 22. PHPPHP/PHP.php
- 23. Execution Pipeline Start Up Request Shut Down SAPI Module Shutdown Engine Shutdown
- 24. Zend/zend.c
- 25. Execution Pipeline Start Up Request Shut Down SAPI Request Init Compile Code Execute Code Request Shutdown
- 28. Lexer Step ● C-PHP ○ Tokenizes using RE2C ○ Produces Array of Tokens ● PHPPHP ○ Uses core tokenizer (or emulative) ○ PHPParser Powered
- 32. Parse Step ● C-PHP ○ Directly Generates OPCode Array ○ BISON Powered ● PHPPHP ○ Generates AST Structure ○ PHPParser Powered
- 35. Compile Step ● C-PHP ○ Compiled Directly During Parse ○ Single Pass Compilation ● PHPPHP ○ Recurses Over AST ○ Single Pass (for now) ○
- 38. OpCodes ● A Series of Operations ○ Just like Assembler Opcodes ○ Represent "units of functionality" ● Designed to run on Virtual Machine ○ Zend Engine ○ Or PHPPHP!
- 39. $a = 1; $b = 2; echo $a + $b;
- 41. Notice Anything?
- 44. What If We Cached The OpCodes?
- 45. We Can Cache! ● Given the compiler is Idempodent ○ (has no side-effects) ○ (hint: it's not) ● OpCodes are really Pointers ○ Swizzling!!!
- 46. In Other Words
- 49. Time To Execute!
- 54. But What Are We Executing?
- 56. Interesting Note: vm_execute.h Is Generated By PHP
- 58. Variables!
- 59. Zend/zend.h
- 62. Ref-Counting ● RefCount + References ○ Allows Copy-On-Write ● Variable Is "Deleted" When RefCount = 0 ● Enables Primitive Garbage Collection ○ Circular GC is also implemented
- 63. That's All There Is To It!
- 65. Let's Look At An Example
- 66. $a = 1; $b = 2; var_dump( $a + $b );
- 67. line # op return operands ----------------------------------- 2 0 ASSIGN !0, 1 3 1 ASSIGN !1, 2 6 2 ADD ~2 !0, !1 3 SEND_VAL ~2 4 DO_FCALL 'var_dump' 5 RETURN 1
- 68. [0] => PHPPHPEngineOpLinesAssign [1] => PHPPHPEngineOpLinesAssign [2] => PHPPHPEngineOpLinesAdd [3] => PHPPHPEngineOpLinesInitFCallByName [4] => PHPPHPEngineOpLinesSend [5] => PHPPHPEngineOpLinesFunctionCall [6] => PHPPHPEngineOpLinesReturnOp
- 69. [0] => PHPPHPEngineOpLinesAssign Object ( [op1] => PHPPHPEngineZvalPtr Object ( [zval:protected] => PHPPHPEngineZvalVariable Object ( [name:protected] => PHPPHPEngineZvalPtr Object ( [zval:protected] => PHPPHPEngineZvalValue Object ( [value:protected] => a [refcount:protected] => 1 [isRef:protected] => [dtorFunc:protected] => ) ) [class:protected] => [zval:protected] => [executor:protected] => [scope] => 1 ) ) [op2] => PHPPHPEngineZvalPtr Object ( [zval:protected] => PHPPHPEngineZvalValue Object ( [value:protected] => 1 [refcount:protected] => 1 [isRef:protected] => [dtorFunc:protected] => ) ) [result] => [lineno] => 2 )
- 78. Get Involved!
- 80. More Info ● github.com/php/php-src ● lxr.php.net ● github.com/ircmaxell/PHPPHP ● Reference Series ○ wiki.php.net ○ blog.ircmaxell.com ■ PHP Internals Series