Slides for my talk "Principles of PHP Package Design" at the Dutch PHP Conference 2014 (http://phpconference.nl).

1. Principles of PHP Package Design
Objectoriented design for packages
Matthias Noback - PHP developer and consultant
Dutch PHP Conference - 6/28/2014

2. Matthias Noback
Noback's Office
PHP developer
Consultant, writer
Proud father
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3. Blog
php-and-symfony.matthiasnoback.nl
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4. A Year With Symfony
leanpub.com/a-year-with-symfony
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5. Tight coupling
Coupling to a framework
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6. Code
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7. Squiggly lines
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8. Code
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9. Packages
There are many different kinds
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10. Class design
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11. Package design
Nothing?
butunclebob.com
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12. Principles of PHP Package Design
leanpub.com/principles-of-php-package-design
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13. Package design
Cohesion
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14. Package design
Coupling
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15. A - Cohesion principles
Perspective: the package in isolation
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16. 1 - The Release Reuse Equivalence Principle
The granule of reuse is the granule of release
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17. 1 - The Release Reuse Equivalence Principle
Version control and hosting
Composer package definition
Meta-files
Auto-loading
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Semantic versioning
Quality control
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Branches
Tags
Backward compatibility
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18. 1 - The Release Reuse Equivalence Principle
If you don't have the time to turn your reusable code into a proper package...
Don't release it.
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19. 2- The Common Reuse Principle
Classes that are used together are packaged together
If you use one class of a package,
you will use all its other classes too.
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20. 2- The Common Reuse Principle
Smell: Feature strata
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21. 2- The Common Reuse Principle
Example of feature strata: the Symfony Security Component
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22. 2- The Common Reuse Principle
Smell: Classes with different dependencies
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23. 2- The Common Reuse Principle
Example of different dependencies: Gaufrette
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24. 2- The Common Reuse Principle
Different dependencies: Gaufrette
{
"name":"knplabs/gaufrette",
...
"suggest":{
"knplabs/knp-gaufrette-bundle":"tousewithSymfony2",
"dropbox-php/dropbox-php":"tousetheDropboxadapter",
"rackspace/php-opencloud":"touseOpencloudadapter",
"herzult/php-ssh":"touseSFtpadapter",
"phpseclib/phpseclib":"tousePhpseclibSftpadapter",
"aws/aws-sdk-php":"tousetheAmazonS3adapter",
"amazonwebservices/aws-sdk-for-php":"tousethelegacyAmazonS3adapters",
"doctrine/dbal":"tousetheDoctrineDBALadapter",
"microsoft/windowsazure":"touseMicrosoftAzureBlobStorageadapter",
"ext-zip":"tousetheZipadapter",
"ext-apc":"tousetheAPCadapter",
...
},
...
} 24/50

25. 2 - The Common Reuse Principle
Leszek Prabucki's response
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26. 3 - The Common Closure Principle
Classes that change together are packaged together
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27. 3 - The Common Closure Principle
Reasons for change
The application's features change
The business rules change
The web framework's best practices change
The persistence library's configuration changes
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28. 3 - The Common Closure Principle
Smell: code for multiple application layers
Web User Interface
Command-line interface
Model
Infrastructure services
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29. B - Coupling principles
Perspective: the package in relation to other packages
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30. 4 - The Acyclic Dependencies Principle
The dependency graph of packages must have no cycles
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31. 4 - The Acyclic Dependencies Principle
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32. Stability
Something is stable if it's resistant to change.
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33. 5 - The Stable Dependencies Principle
An irresponsible package
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34. 5 - The Stable Dependencies Principle
A dependent package
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35. 5 - The Stable Dependencies Principle
An instable package: irresponsible and dependent
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36. 5 - The Stable Dependencies Principle
A responsible package
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37. 5 - The Stable Dependencies Principle
An independent package
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38. 5 - The Stable Dependencies Principle
A stable package: responsible and independent
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39. 5 - The Stable Dependencies Principle
Depend in the direction of stability
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40. 5 - The Stable Dependencies Principle
Counter example
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41. 6 - The Stable Abstractions Principle
What is more likely to change?
Something concrete or something abstract?
A class or an interface?
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42. 6 - The Stable Abstractions Principle
Abstractness should increase with stability
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43. Summary
Reuse/release equivalence principle
Common reuse principle
Common closure principle
Acyclic dependencies principle
Stable dependencies principle
Stable abstractions principle
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Reuse only code that you can release as a product.-
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All code in a package is reused at the same time.-
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Code in a package only changes for a few reasons.-
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No cycles in the dependency graph.-
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Only depend on more stable packages.-
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More stable packages are also more abstract.-
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44. Word of advice
You can't maximize them all at the same time.
Keep them in mind while you are working on a package.
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45. Principles of PHP Package Design
leanpub.com/principles-of-php-package-design
I'm impressed. — Robert C. Martin
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46. Principles of PHP Package Design
Get a 10 dollar discount:
http://leanpub.com/principles-of-php-package-design/c/dpc2014
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47. Questions?
feedback joind.in/10883
twitter @matthiasnoback
leanpub leanpub.com/principles-of-php-package-design
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48. Image courtesy
Clean Coders
GitHub
BitBucket
Packagist
PoEAA
But Uncle Bob
Robert Martin
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49. 50/50