Managing the Software Life
Cycle of PHP Applications
Stefan Priebsch, e-novative GmbH
php|works 2008, Atlanta, GA

About Me
● Stefan Priebsch
● From Munich, Germany
● Degree in computer science
● PHP enthusiast since PHP 4.0b3
● Consultant, Trainer, Author
● I help customers make better use of PHP

Who are you?

Software Lifecycle

Software Lifecycle
ve
si
● Inception
ur
● Elaboration
c
Re
● Construction
Transition
tly
●
● Production en
● Retirement
h er
In

„The perfect project plan is
possible if one first documents
a list of all the unknowns“
-- Bill Langley

Process Models

Waterfall Model
● Systems Engineering
● Analysis
● Design
● Coding
● Testing
● Deployment and maintenance

„The most important single aspect of
software development is to be clear
about what you are trying to build“
-- Bjarne Stroustrup

„Life can only be
understood backwards,
but it must be lived forwards“
-- Soren Kierkegaard

Other Models
● V-Model
● Spiral Model
● Rational Unified Process
● Extreme Programming
● Scrum
● Test-driven Development
● ...

Linear Processes Fail

Iterative Processes Win

„The name of a Type instance is
a Name instance representing
the name of the Type;
its value may not be a null name [...]
The name of an Instance instance is
optional, but where it exists it must not
be a null name [...]
An Instance instance with no name is
always considered to have a unique
name, distinct from any other Instance
instance with no name.“
-- Rational UML Document Set,
Semantics, Chapter 5.2

„There's no sense being exact about
something if you don't even know
what you're talking about“
-- John von Neumann

Heavy Processes Fail

Lightweight Wins

Agile Methods
● Individuals and interactions
over processes and tools
● Working software
over comprehensive documentation
● Customer collaboration
over contract negotiation
● Responding to change
over following a plan

Agile Development
● Working software is delivered
frequently
● Working software is the principal
measure of progress
● Even late changes in requirements
are welcomed
● Regular adaptation to changing
circumstances

Small Incremental Steps

„Complexity kills.
It sucks the life out of developers,
it makes products difficult to plan,
build and test, it introduces security
challenges and it causes end-user
and administrator frustration“
-- Ray Ozzie

Reuse
● Stick to standards
● Open source = open knowledge
● Reuse Experience
● Use Components
● Use Frameworks?

Basic Quality Assurance
● Static Code Analysis
● Lint (php -l)
● PHP_CodeSniffer
● Software Metrics
● PHPUnit
● PHP_Depend
● Output validation
● Tidy
● HTML/CSS validation

PHP_CodeSniffer
FILE: /path/to/code/myfile.php
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
FOUND 5 ERROR(S) AFFECTING 5 LINE(S)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
2 | ERROR | Missing file doc comment
20 | ERROR | PHP keywords must be lowercase; expected \"false\" but found \"FALSE\"
47 | ERROR | Line not indented correctly; expected 4 spaces but found 1
51 | ERROR | Missing function doc comment
88 | ERROR | Line not indented correctly; expected 9 spaces but found 6
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
FILE: /path/to/code/yourfile.php
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
FOUND 1 ERROR(S) AND 1 WARNING(S) AFFECTING 1 LINE(S)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
21 | ERROR | PHP keywords must be lowercase; expected \"false\" but found
| | \"FALSE\"
21 | WARNING | Equals sign not aligned with surrounding assignments
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

PHP_Depend

„Measuring programming progress by
lines of code is like measuring aircraft
building progress by weight“
-- Bill Gates

Testing
● Unit Tests
● Integration Tests
● System Tests
● Acceptance Tests
● Testing Tools:
● PHPUnit
● Selenium

„A fault discovered and corrected in the
unit testing phase is more than a
hundred times cheaper than if it is
done after delivery to the customer.“
-- Barry Boehm

Deployment
● svn checkout
● Compressed archive (tar.gz, zip, bzip2)
● PEAR installer
● New in PHP 5.3: phar archives
● rsync

Deployment
● Always automate deployment
● Use 3 Systems
● Development
● Integration/Staging
● Live
● Consider virtual machines

Continuous Integration
● Automate builds
● Integrate frequently
● Run automated tests
● Tools:
● CruiseControl
● phpUnderControl

Continuous Integration

Debugging
● Create a test to expose each bug
● Keep the test, and run it often
● Tool: xdebug
● Tracing
● Remote Debugging

„Debugging is twice as hard as
writing the code in the first place.
Therefore, if you write
the code as cleverly as possible,
you are, by definition,
not smart enough to debug it“
-- Brian W. Kernighan

Maintenance

„The cost of adding a feature isn't just
the time it takes to code it. The cost
also includes the addition of an
obstacle to future expansion“
-- John Carmack

„Large-program structure must not
only be created but must also be
maintained if decay is to be avoided
or postponed“
-- Meir Lehman

Refactoring
● Improve the design of software without
changing its behaviour
● „Clean up“ code
● Not adding new features
● Keep refactoring your code constantly
● Use unit tests to ensure you don't
break anything

„You know you've achieved
perfection in design, not when you
have nothing more to add, but when
you have nothing more to take away“
-- Antoine de Saint-Exupery

Scaling
● Do not guess where to start
● Profile your code
● how often are functions called
● how long does execution take
● ! that's just one execution path
● Tool: xdebug

„Premature optimization
is the root of all evil“
-- Donald Knuth

How to scale
● Reduce I/O
● Disks are slow
● Network is slow
● Caching
● Bytecode caching
● Data caching
● Result caching

Migration
● Code E_STRICT-compatible
● in PHP 5.3: watch out for E_DEPRECATED
● Compare trace logs between versions
● Refactor when fixing issues

Today's Take-Aways

Today's Take-Aways
● Keep things simple
● Accept change
● Test early and often
● Automate tests and deployment

„It's not at all important
to get it right the first time.
It's vitally important
to get it right the last time“
-- Andrew Hunt and David Thomas

Thank you.

http://www.priebsch.de
stefan.priebsch@e-novative.de
Profiles at Xing, LinkedIn, Facebook