php internals
TRANSCRIPT
PHP Internals
Nico LoubserDeveloper at …..
“One night only” Curriculum.
Focus on concepts that will allow you to build things.
Lexical analysis
Syntax analysis [PHP7]
Opcode
Extensions
And some interesting facts about PHP
Terminology
1. Zvals are the datastructures holding PHP variable data. Variable points to a
Zval
2. A Reference !== Passing by reference. Reference === `Points`
3. Variables references zvals
4. Heap is the memory where zvals live
PHP Execution
Interpreted, compiled, or both?
These are the typical steps of a multipass compiler
- Lexical analysis
- Syntax analysis
- Some other steps maybe….
- Opcode [Final compilation]
Lexical analysis
Step one. Converts a script into tokens by Zend’s token engine. Really? Yes
really.
Lexical analysis. What does tokenized data look like?
Lexical analysis - can we use it for anything?
Source code highlighting and other tools.
Syntax analysis
PHP 7 introduced AST
More maintainable parser and compiler
Decoupling syntax decisions from technical issues
AST - parse tree for PHP script. [ https://github.com/nikic/PHP-Parser ]
AST - Generated code
AST - Generated code
Opcode
VLD / Bytekit / Parsekit
I used VLD, easiest to get to work.
Vulcan Logic Disassembler
Bytekit doesn’t seem to be supported, Parsekit results same is VLD.
Vulcan Logic Disassembler
ZVALS
How PHP represents data and keeps count of references for instance.
Represented by a C type called a Union.
PHP5
Zvals
The important difference between PHP 5 and PHP 7 : share the same Zval, regardless of by value or
reference.
Only once some kind of modification is performed the array will be separated.
Simulation of the copy-on-write behavior
Time to run some scripts…..
[Script can be found in github]
Extension
The hard way.
The PHP way.
The C++ way.
Extensions
I used the PHP-CPP skeleton framework. http://www.php-cpp.com/
You will need sudo apt-get install php5-dev
In Makefile
Assign your extension name to the NAME parameter, and then create a ini file with the same name.
Put this in the ini file
extension=quintillion.so
Make && make install
Run php -i | grep quintillion
/etc/php5/cli/conf.d/quintillion.ini
Comparison of normal vs extension
Live long and prosper
Internals is very interesting topic.
Knowledge about internals is good for memory, good for speed, data-structures, native implementations to interface with something.
@Nico_Loubser