PHP, Under The Hood - DPC
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The document provides an overview of PHP, highlighting its characteristics such as being dynamically and weakly typed, and its compilation process via different implementations. It describes the PHP execution pipeline, the lexer and parser stages, and explains how opcodes function within the language. Additionally, it touches on memory management aspects like reference counting and garbage collection, along with resources for further exploration of PHP internals.
![[0] => PHPPHPEngineOpLinesAssign
[1] => PHPPHPEngineOpLinesAssign
[2] => PHPPHPEngineOpLinesAdd
[3] => PHPPHPEngineOpLinesInitFCallByName
[4] => PHPPHPEngineOpLinesSend
[5] => PHPPHPEngineOpLinesFunctionCall
[6] => PHPPHPEngineOpLinesReturnOp](https://image.slidesharecdn.com/phpunderthehood-dpc-130607073657-phpapp01/85/PHP-Under-The-Hood-DPC-68-320.jpg)
![[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
)](https://image.slidesharecdn.com/phpunderthehood-dpc-130607073657-phpapp01/85/PHP-Under-The-Hood-DPC-69-320.jpg)
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