GAP: G eneric A spects for P HP Sebastian Bergmann Günter Kniesel <sb@ez.no> <gk@cs.uni-bonn.de> 3 rd European Workshop on Aspects in Software University of Twente, Enschede, The Netherlands August 31, 2006

Sebastian Bergmann Günter Kniesel

<sb@ez.no> <gk@cs.uni-bonn.de>

The dominant programming language in Web-based development. Easy to learn. Designed for the Web. Good performance, low resource consumption. Excellent scaling capabilities, shared-nothing architecture. “ When it comes to the Web and Web applications, Java is not the right language. PHP is to 2005 what Java was to 1995.”, Marc Andreessen, founder of Netscape Inc. PHP

The dominant programming language in Web-based development.

Easy to learn.

Designed for the Web.

Good performance, low resource consumption.

Excellent scaling capabilities, shared-nothing architecture.

“ When it comes to the Web and Web applications, Java is not the right language. PHP is to 2005 what Java was to 1995.”, Marc Andreessen, founder of Netscape Inc.

Language Features Supports both the procedural and object-oriented programming paradigms. Mixing them is possible and encouraged. Feature-rich, class-based object model. Native support for XML and other Web technologies. Interpreter designed for extensibility. Increasingly used outside its original Web context (CLI, Gtk+, Qt). PHP

Language Features

Supports both the procedural and object-oriented programming paradigms. Mixing them is possible and encouraged.

Feature-rich, class-based object model.

Native support for XML and other Web technologies.

Interpreter designed for extensibility.

Increasingly used outside its original Web context (CLI, Gtk+, Qt).

Example of PHP Base Code

GAP G eneric A spects for P HP. Generic Join Point model for PHP. Framework to implement custom pointcut system. Aspect Generic ity. Advice = Plain PHP method. Inside this method, the same information is available that is used by GAP for advice dispatching. Sample pointcut system uses annotations in code comments to connect join points to aspect effects .

G eneric A spects for P HP.

Generic Join Point model for PHP.

Framework to implement custom pointcut system.

Aspect Generic ity.

Advice = Plain PHP method.

Inside this method, the same information is available that is used by GAP for advice dispatching.

Sample pointcut system uses annotations in code comments to connect join points to aspect effects .

GAP Join Points Object Initialization Field Access Method Call / Method Execution Aspect Effects Advice Intertype-Declarations Custom Errors

Join Points

Object Initialization

Field Access

Method Call / Method Execution

Aspect Effects

Advice

Intertype-Declarations

Custom Errors

GAP Sample Pointcut System initialization( class ( parameters )) get( modifier class -> attribute ) set( modifier class -> attribute ) method( modifier class -> method ( parameters )) source( modifier class -> method ( parameters )) cflow( modifier class -> method ( parameters ))

Sample Pointcut System

initialization( class ( parameters ))

get( modifier class -> attribute )

set( modifier class -> attribute )

method( modifier class -> method ( parameters ))

source( modifier class -> method ( parameters ))

cflow( modifier class -> method ( parameters ))

A GAP Aspect

A GAP Aspect

Generic Aspects Aspect languages introduce strong dependencies of aspect code on base code. The use of concrete names of base code entities in pointcut expressions is required. Wildcards such as * and .. are intended to alleviate this problem but are too general. They match more than intended because it is not possible to express dependencies of the values matched by different wildcards.

Aspect languages introduce strong dependencies of aspect code on base code.

The use of concrete names of base code entities in pointcut expressions is required.

Wildcards such as * and .. are intended to alleviate this problem but are too general.

They match more than intended because it is not possible to express dependencies of the values matched by different wildcards.

Generic Aspects Generic aspect languages such as LogicAJ replace wildcards (e.g. * ) by named logic meta-variables (e.g. ?var ). All occurrences of ?var in a pointcut expression must match the same value. Further constraints on the legal matches can be expressed by additional predicates that can be used in pointcut definitions.

Generic aspect languages such as LogicAJ replace wildcards (e.g. * ) by named logic meta-variables (e.g. ?var ).

All occurrences of ?var in a pointcut expression must match the same value.

Further constraints on the legal matches can be expressed by additional predicates that can be used in pointcut definitions.

A Generic GAP Aspect

Existing AOP Solutions for PHP Preprocessor PHPAspect, AOPHP Aspect-Aware PHP Interpreter aspectPHP Meta-Programming AOP Library for PHP Dependency Injection Container Seasar2

Preprocessor

PHPAspect, AOPHP

Aspect-Aware PHP Interpreter

aspectPHP

Meta-Programming

AOP Library for PHP

Dependency Injection Container

Seasar2

Implementation of GAP Uses PHP's streams system and Runkit extension to introduce generic hooks and weave inter-type declarations into PHP bytecode at load-time. Generic hooks activate advice at runtime.

Uses PHP's streams system and Runkit extension to

introduce generic hooks and

weave inter-type declarations

into PHP bytecode at load-time.

Generic hooks activate advice at runtime.

Implementation of GAP Class Sources Aspect Sources Interception of loaded PHP source Source-Level Transformation Normal Compilation

Implementation of GAP Bytecode-Level Transformation

Conclusion GAP Implementation of aspect-oriented programming for PHP. Uses dynamic weaving Supports aspect genericity. Provides a framework to implement custom pointcut languages on top of it.

GAP

Implementation of aspect-oriented programming for PHP.

Uses dynamic weaving

Supports aspect genericity.

Provides a framework to implement custom pointcut languages on top of it.