Principles of PHP Package DesignObject oriented design for packages

Matthias Noback - PHP developer and consultantDutch PHP Conference - 6/28/2014

Matthias NobackNoback's Office

PHP developerConsultant, writerProud father

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Blogphp-and-symfony.matthiasnoback.nl

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A Year With Symfony

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Tight couplingCoupling to a framework

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Code

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Squiggly lines

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Code

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PackagesThere are many different kinds

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Class design

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Package designNothing?

butunclebob.com

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Principles of PHP Package Design

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Package designCohesion

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Package designCoupling

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A - Cohesion principlesPerspective: the package in isolation

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1 - The Release Reuse Equivalence PrincipleThe granule of reuse is the granule of release

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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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BranchesTagsBackward compatibility

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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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2- The Common Reuse PrincipleClasses 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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2- The Common Reuse PrincipleSmell: Feature strata

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2- The Common Reuse PrincipleExample of feature strata: the Symfony Security Component

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2- The Common Reuse PrincipleSmell: Classes with different dependencies

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2- The Common Reuse PrincipleExample of different dependencies: Gaufrette

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2- The Common Reuse PrincipleDifferent dependencies: Gaufrette

{ "name": "knplabs/gaufrette", ... "suggest": { "knplabs/knp-gaufrette-bundle": "to use with Symfony2", "dropbox-php/dropbox-php": "to use the Dropbox adapter", "rackspace/php-opencloud" : "to use Opencloud adapter", "herzult/php-ssh": "to use SFtp adapter", "phpseclib/phpseclib": "to use PhpseclibSftp adapter", "aws/aws-sdk-php": "to use the Amazon S3 adapter", "amazonwebservices/aws-sdk-for-php": "to use the legacy Amazon S3 adapters", "doctrine/dbal": "to use the Doctrine DBAL adapter", "microsoft/windowsazure": "to use Microsoft Azure Blob Storage adapter", "ext-zip": "to use the Zip adapter", "ext-apc": "to use the APC adapter", ... }, ...} 24/50

2 - The Common Reuse PrincipleLeszek Prabucki's response

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3 - The Common Closure PrincipleClasses that change together are packaged together

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3 - The Common Closure PrincipleReasons for change

The application's features changeThe business rules changeThe web framework's best practices changeThe persistence library's configuration changes...

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3 - The Common Closure PrincipleSmell: code for multiple application layers

Web User InterfaceCommand-line interfaceModelInfrastructure services

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B - Coupling principlesPerspective: the package in relation to other packages

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4 - The Acyclic Dependencies PrincipleThe dependency graph of packages must have no cycles

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4 - The Acyclic Dependencies Principle

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Stability

Something is stable if it's resistant to change.

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5 - The Stable Dependencies PrincipleAn irresponsible package

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5 - The Stable Dependencies PrincipleA dependent package

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5 - The Stable Dependencies PrincipleAn instable package: irresponsible and dependent

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5 - The Stable Dependencies PrincipleA responsible package

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5 - The Stable Dependencies PrincipleAn independent package

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5 - The Stable Dependencies PrincipleA stable package: responsible and independent

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5 - The Stable Dependencies PrincipleDepend in the direction of stability

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5 - The Stable Dependencies PrincipleCounter example

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6 - The Stable Abstractions PrincipleWhat is more likely to change?

Something concrete or something abstract?A class or an interface?

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6 - The Stable Abstractions PrincipleAbstractness should increase with stability

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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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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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Principles of PHP Package Design

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I'm impressed. — Robert C. Martin

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Principles of PHP Package Design

Get a 10 dollar discount:

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Questions?

feedback joind.in/10883

twitter @matthiasnoback

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Image courtesy

Clean CodersGitHubBitBucketPackagistPoEAABut Uncle BobRobert Martin

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