So gelingt der Umstieg von PHP4 auf PHP5: Erneuerung von Geschäftsanwendungen unter Qualitätsaspekten

So gelingt der Umstieg von PHP4 auf PHP5: Erneuerung von Geschäftsanwendungen unter Qualitätsaspekten

Lars Jankowfsky, CTO, swoodoo GmbH

Lars Jankowfsky?

Lars Jankowfsky, swoodoo.com

• Software Architect, CTO seit 1992• PHP seit 1998• Viele erfolgreiche Projekte von 2 bis 20

Entwickler.• CTO and (Co)Founder swoodoo.com• (Co)Founder of OXID eSales. Refactored

OXID eShop during 1.5 years with 10 developers.

What about your projects?

- What‘s your average project lifetime?

- Is there PHP code more than 5 years old?

- How many lines of code?

- How many change requests per year?

- Has there been a specification?

- Were all features in the first released version implemented like they‘re specified in the specification?


Jankowfsky, Rinne – Mayflower/swoodoo

Legacy Code?

Wikipedia says „Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer technology. The term can also mean code inserted into modern software for the purpose of maintaining an older or previously supported feature“


• MySQL 4 support will end • Active support already ended by the end of 2006• Only extended support until 2008 for MySQL 4.0 and

2009 for MySQL 4.1• MySQL 5 has more and advanced features like stored

procedures, trigger, better SQL support• PHP 4 support did end

• PHP 4 is dead, dead, dead• Only security relevant fixes until 2008-08-08• PHP 5.2 is faster and more stable than every PHP 4

version• PHP 5.3 upcoming

Why upgrade?

Why upgrade?

- change requests get more and more expensive

- bug rate is increasing

- clearly a dead-end street!

- team motivation decreases

- hard to bring in new members into the team

- deprecated functions cause problems in future PHP releases


Typical problems?

- Typical legacy applications

- Started some years ago with PHP 4

- written in Spaghetti code

- half procedual, half object-orientated

- „PHP 4“ OOP

- using old, unmaintained libraries like PEAR::DB


PHP, made in 2000

- no coding standards

- no PHPDoc

- no Design Patterns

- few separation of concerns

- has been changed a lot

- no refactoring, because „it worked“

- updated to run with php 4 in 2003

- updated to run with php 5 in ... ?


PHP 4 OOP - strategy

- Maybe you‘re lucky and there are no problems. Maybe.

- If you see problems, they are fatal errors like - Objects are referenced by value - $foo =& new Foo();

- Solution: - Use standard APIs - Fix the PHP 5 problems


„Half procedual –halb object-orientated“

- Code with different quality

- Just a few documentation

- Maybe some tests ... maybe ...

- „the typical current PHP 4 project“

- Found everywhere! Really everywhere!


„Half procedual –half object-orientated“ - strategy

- Add inline documentation for all classes and methods

- Improve the re-using of duplicate code

- Improve every code part with PHP 5 functions, for example using file_put_contents() instead of fopen(), fwrite(), and fclose().


Spaghetti Code?

- Very old code, maybe developed in the last PHP 3 century

- a lot of redundant copy-paste code

- missing separation of concerns

- No or just minor separation of code and layout

- No use of libraries like PEAR, Zend Framework or eZ components

- No or outdated documentation

- No tests at all


Spaghetti Code - strategy

- Identify recurring code parts and implement classes

- Use of standard libraries like Zend Framework or eZ components

- Add inline documentation

- Fix your coding styles!



- No new features

- No technical changes like new database layer

or new template engine

- No influences for productive services like External systems

- Minimization of time and effort

Requirements

What you should never do!

Please don‘t try a complete rewrite!

- Too expensive

- Takes too long

- the old codebase is used, tested & bugfixed

- Developers love to rewrite:new code is more fun, code is easier to write than to read


Remember?

Jankowfsky, Rinne – Mayflower/swoodoo

Netscape 6? Rewrite....

dBase for Windows? Rewrite....

Quattro Pro? Rewrite....

Access refatored...

Excel

Porting


Rewrite

Reengineering

Porting

complexity

Innovation potential

posit

ive

nega

tive

What is porting?


• Reasons• Most simple form of migration• Manageble risks• Small complexity because of the lack of

qualitive and technical changes• Requirement

• Minor differences between current and future application platform

What is porting?


Refactoring


Refactoring?

- Modifying code without changing it‘s behaviour

- „cleaning up“

“Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure.” (Martin Fowler)


Modifying without... ?????

- if you refactor you need tests to proove that you did not break any functionality

- Have tests first. Then change code.

- legacy code ? There are no tests!!


And now ?

- Write tests first.

- You will need to refactor your application while writing tests.

- Write selenium tests for your application. - no :(



• Targets• Porting without any technical or qualitative

changes• Recovery of support (MySQL/PHP)• Minimizing the interferences of services and

reduction of change times• Interferences

• Porting problems between MySQL and PHP versions

• Application complexity • missing documentation and missing contact

persons• Communication between all team members

Preparations


- Reducing of complexity with a planned procedure

- Coverage of the complete porting

- Methodical description of the process

Process model

How do we start?

- Identify the nastiest, ugliest and...

- probably most important piece of code and let‘s start with this one.

- if you take the easy files you won‘t solve the critical issues and...

- move the risk to the end.


While porting ...

- adjust coding style

- add missing documentation

- remove redundant code / copy & paste-code

- remove unused(!) code

- maintain a list of future todos with priorities


PHP and Unit Testing

- Layout & UI code is hard to unit-test, acceptance-test instead

- test maintenance costs:- unit test work fine with stable APIs- high change rate in PHP results in API changes- tests need to be changed, too

- slows down development, increases initial development costs

- ... but your software survives more than 4 years


Test Driven Adoption

1. Unit tests for existing code with PHPUnit

2. experience of confidence in own code

3. Insight: Tests are easier if written before software

4. Insight: Tests help documenting the code

5. Insight: Tests define the real API


Tools?

- CruiseControl for continous integration- PHPUnit- SeleniumRC and SeleniumIDE

- PHP Code Sniffer- PHP CodeBrowser


Golden rules

- know your budget: what are your maintenance costs? What are the things you can‘t do now?

- there is no silver bullet. It takes time.

- Confident developers are efficient developers

- There is no way around proper coding style and documentation


Questions?


Thank you for your interest!

eMail: [email protected]


mailto:[email protected]

mailto:[email protected]

Technology

So gelingt der Umstieg von PHP4 auf PHP5: Erneuerung von Geschäftsanwendungen unter Qualitätsaspekten