Aspect-Oriented Programming for PHP

phpAspect A spect- O riented P rogramming William Candillon { [email_address] }

O verview
Acknowledgment
Introduction to AOP
phpAspect
New features
Conclusion

A cknowledgment
Gilles Vanwormhoudt ( [email_address] )
PhD in computer science at Telecom Lille
Collaborator on the phpAspect project
Yijun Yu ( [email_address] )
PhD in computer science, University of Toronto
Author of Yaxx
Sebastian Bergmann ( [email_address] )
Diploma Thesis, University of Bonn.
Google soc mentor

P rogramming evolution

Introduction to AOP

O bject- O riented P rogramming
Advantages
Business modeling
Reusable technicals components
Design patterns
Frameworks
Vertical organization
Inheritance and interfaces
Objects graph

T echnicals aspects in OOP

S ymptoms
Inheritance can't modularize horizontal concerns
Code Tangling
Code scattering
Difficulties
Code comprehension
Code reusability
Code evolution

A spect- O riented P rogramming
A new programming paradigm...
Working with OOP
Split technicals concerns from the business logic
...defining mechanisms for
Writing aspects as a new software entity
Wrapping crosscutting concerns
Coating business logic with technicals concerns

G eneral idea
Inversion of technicals dependencies

J oinpoints
Identified instructions in the program flow:
Method execution (1)
Attribute writing/reading (2)
Objects construction (3)
Method call (4)
Objects destruction (5)
Exception throwing (6)
A pointcut is a logical association of joinpoints
1 2 3 4 5 6

C ode advices
Injected code in pointcuts
3 types:
Before
Around
After
Aspect and joinpoint reflection to explore the context
Methods, arguments, targeted object etc...

I nter-type declarations
Inter-type attributes
Inter-type constants
Inter-type methods

W ildcards and operators
* denotes any method visibility, method scope, class name, method name or parameters number.
+ denotes type or any subclass or subinterface of a given type in a join point .
The || offers the possibility to combine join points in an advice declaration.

S imple persistence example
Business logic
Aspect

phpAspect

PHP
A highly dynamic language...
Easy to learn
Object-Oriented
Mainly designed for web applications
Used in more than 25 millions of websites.
...more and more used outside its web context
Rapid prototyping
PHP-GTK applications
Command-Line interpreter

S tate of the art in PHP
phpAspect
Static approach
Compiler architecture (Lex/Yacc)
Seasar
Dynamic approach
Using PHP containers
GAP, by Sebastian Bergmann
Only conceptual for now
Other projects: AOPHP, aspectPHP, AOP Library for PHP etc...

A virtual cart
A client add products in the cart.
Business logic without any technicals concerns.

A logging aspect
Log every added articles and give status of the order
After weaving
Result

A security aspect
Make a filter on the customer input
Protection against cross scripting injection
Result

S ingleton aspect
All singletons are factorized in the same aspect
The link between a class and its singleton is null

C urrent weaving chain

New features

N ew weaving chain

F eatures coming very soon
Logicals operators:
Enum operator:
New joinpoints
Reusable aspects mechanisms (with Smarty)
Aspect introspection

W eb specifics joinpoints
PHP has a lot of globals variables with very sensitives informations:
$_GET, $_POST, $_COOKIE, $_SERVER, $_SESSION
We need to intercept writing/reading of these for security matters.
File joinpoint

P ersistence with phpAspect
There is great tools existing for object persistence: Propel for example
Problem: If you regenerate the classes, you lose your businesses operations
Solution: generate an aspect of persistence with Propel from an aspect template and classes annotations

A spect DOM
XPath is a way better than SQL for queries on tree structure.
By weaving DOM interfaces we can use Xpath expressions on:
your object graph
in a visitor design pattern
SQL Query : SELECT * FROM book, books, author WHERE books.idbook = {$_SESSION['id']} AND book.id = books.idbook AND book.author = author.id AND author.name = 'Alexandre Jardin'
Xpath query : //author[@name = 'Alexandre Jardin']

A spects templates (1/2)
Put parameters on aspects with Smarty
A way to define generic and reusables aspects.
Parameters based on the XML format.
Aspect template construction:
Parameters evaluation with Smarty
Result: an aspect ready to be weaved

A spects templates (1/2)
XML parameters:
Template:

L imitations
Aspects composition
Static weaving
Debugging
There is no PHP IDE having AOP features

C onclusion
phpAspect:
Wiki: http://phpaspect.org
Blog: http://wcandillon.blogspot.com
Perspectives:
PHP 6 ready (namespaces)
Aspect composition
Type inference
Framework integration
Looking for an internship: http://wcandillon.netcv.org

R eferences
AOSD community and projects: http://aosd.net
AspectJ in action , by Ramnivas Laddad
Mastering AspectJ , by John & Wiley, Joseph D. Gradecki, Nicholas Lesiecki
Programmation Orientée Aspect pour Java , by Renaud Pawlak, Jean-Philippe Retaillé et Lionel Seinturier.

Questions ?

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Aspect-Oriented Programming for PHP

by William Candillon

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