Download - PHP, Under The Hood - DPC
PHPUnder The Hood
What Is PHP?● An Easy To Learn Language?
○ Sure!● A Simple Language?
○ Usually● A Well Designed Language?
○ HA!● An Effective Language!
○ Absolutely!
PHP Is...
Dynamically Typed
$a = 1;$b = "a";
PHP Is...
Weak Typed
1 + "1b" == 2
PHP Is...
Implementation Defined
ImplementationsMain:
C-PHP: www.php.netAlt:
HipHop - FacebookRoadsend - CompilerPhalanger - .NETPHP Compiler - CompilerPHPPHP - PHP
Interesting Note:C-PHP Requires PHP To Compile!
PHP Is...
Compiled
PHP Is...
DynamicallyCompiled
On-Demand
It All Starts With TheSAPI
SAPI● Server API● "Starts" PHP and issues request(s)● Common SAPIs:
○ CLI○ CGI (and FastCGI)○ mod_php○ FPM○ etc...
Execution Pipeline
Execution PipelineStart Up
Request
Shut Down
SAPI
Execution PipelineStart Up
Request
Shut Down
SAPIConfig Init
Engine Init
Module Init
Zend/zend.c
PHPPHP/PHP.php
Execution PipelineStart Up
Request
Shut Down
SAPI
Module Shutdown
EngineShutdown
Zend/zend.c
Execution PipelineStart Up
Request
Shut Down
SAPI
Request Init
Compile Code
Execute Code
Request Shutdown
Compiler PipelineLexer
Lexer Step● C-PHP
○ Tokenizes using RE2C○ Produces Array of Tokens
● PHPPHP○ Uses core tokenizer (or emulative)○ PHPParser Powered
Zend/zend_language_scanner.l
PHPParser/Lexer/Emulative.php
Compiler PipelineLexer
Parser
Parse Step● C-PHP
○ Directly Generates OPCode Array○ BISON Powered
● PHPPHP○ Generates AST Structure○ PHPParser Powered
Zend/zend_language_parser.y
Compiler PipelineLexer
Parser
Compiler
Compile Step● C-PHP
○ Compiled Directly During Parse○ Single Pass Compilation
● PHPPHP○ Recurses Over AST○ Single Pass (for now)○
PHPPHP/Engine/Compiler.php
Compiler PipelineLexer
Parser
Compiler
OpCode
OpCodes● A Series of Operations
○ Just like Assembler Opcodes○ Represent "units of functionality"
● Designed to run on Virtual Machine○ Zend Engine○ Or PHPPHP!
$a = 1;$b = 2;echo $a + $b;
Notice Anything?
What If We Cached The OpCodes?
We Can Cache!● Given the compiler is Idempodent
○ (has no side-effects)○ (hint: it's not)
● OpCodes are really Pointers○ Swizzling!!!
In Other Words
OpCode CachingIs Hard!
Time To Execute!
Zend/zend_vm_execute.h
PHPPHP/Engine/Executor.php
Executor Pipeline
OpCode
Is Return?No Yes
Return
But What Are We Executing?
Zend/zend_vm_execute.h
Interesting Note:vm_execute.h
Is Generated By PHP
PHPPHP/Engine/OpLines/Add.php
Variables!
Zend/zend.h
PHPPHP/Engine/Zval/Value.php
Ref-Counting● RefCount + References
○ Allows Copy-On-Write● Variable Is "Deleted" When
RefCount = 0
● Enables Primitive Garbage Collection○ Circular GC is also implemented
That's All There Is To It!
Let's Look At An Example
$a = 1;$b = 2;var_dump( $a + $b);
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
[0] => PHPPHP\Engine\OpLines\Assign[1] => PHPPHP\Engine\OpLines\Assign[2] => PHPPHP\Engine\OpLines\Add[3] => PHPPHP\Engine\OpLines\InitFCallByName[4] => PHPPHP\Engine\OpLines\Send[5] => PHPPHP\Engine\OpLines\FunctionCall[6] => PHPPHP\Engine\OpLines\ReturnOp
[0] => PHPPHP\Engine\OpLines\Assign Object (
[op1] => PHPPHP\Engine\Zval\Ptr Object (
[zval:protected] => PHPPHP\Engine\Zval\Variable Object (
[name:protected] => PHPPHP\Engine\Zval\Ptr Object (
[zval:protected] => PHPPHP\Engine\Zval\Value Object (
[value:protected] => a
[refcount:protected] => 1
[isRef:protected] =>
[dtorFunc:protected] =>
)
)
[class:protected] =>
[zval:protected] =>
[executor:protected] =>
[scope] => 1
)
)
[op2] => PHPPHP\Engine\Zval\Ptr Object (
[zval:protected] => PHPPHP\Engine\Zval\Value Object (
[value:protected] => 1
[refcount:protected] => 1
[isRef:protected] =>
[dtorFunc:protected] =>
)
)
[result] =>
[lineno] => 2
)
PHPPHP/Engine/OpLines/Assign.php
PHPPHP/Engine/OpLines/Add.php
PHPPHP/Engine/OpLines/InitFCallByName.php
PHPPHP/Engine/OpLines/Send.php
PHPPHP/Engine/OpLines/FunctionCall.php
There's A Ton More
Get Involved!
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
