Enterprise PHP Patterns

Stefan Priebsch, e-novative GmbH

„ Every pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over,without ever doing it the same way twice.“ (Christopher Alexander)

Software Design Patterns Are

Blueprints for proven solutions

A common language for developers

Useful to understand frameworks

They Are Not

The solution to all design problems

Ready-made implementations

Magic bullets

Basic Patterns

Map

Registry

Singleton

Subject/Observer

Iterator

Factory

public function fooFactory() { return new Foo(); }

Factory With Testmode

public function fooFactory() { if (TESTMODE) { return new FooTest(); } else { return new Foo(); } }

RequestHelper

Registry

Stores input data

Decouples application from superglobals

Centralized filtering/sanitation

Makes testing easier

RequestHelper

class RequestHelper { protected $get = array(); protected $post = array(); protected $cookies = array(); public function __construct($aGet, $aPost, $aCookies) { $this->get = $aGet; $this->post = $aPost; $this->cookies = $aCookies; } public function getGetValue($aKey) public function getPostValue($aKey) public function getCookieValue($aName) public function hasCookie($aName) }

Filtering RequestHelper

class FilteringRequestHelper { protected $get = array(); protected $post = array(); protected $cookies = array(); public function __construct($aGet, $aPost, $aCookies) { $this->get = $this->filter($aGet); $this->post = $this->filter($aPost); $this->cookies = $aCookies; } public function getGetValue($aKey) public function getPostValue($aKey) public function getCookieValue($aName) public function hasCookie($aName) }

Command

Encapsulates a task

Selects a view

Allows command chaining

Support undoable commands

Command

class Command { public function execute() }

Validating Command

class Command { protected function validate() protected function doExecute() public function execute() { if ($this->validate()) { $this->doExecute(); } } }

Command Selecting View

class Command { protected $view; public function execute() { if ($this->validate()) { $this->doExecute(); $this->view = new SuccessView(); } else { $this->view = new ErrorView(); } return $this->view->display(); } }

Chained Command

class ChainedCommand { protected function doExecute() { $cmd = new FirstCommand(); $cmd->execute(); $cmd = new SecondCommand(); $cmd->execute(); $cmd = new ThirdCommand(); $cmd->execute(); } }

Domain Model

Business objects encapsulating data and behaviour

Similar to E/R model, but with methods and inheritance

Keep business logic separate from data access and presentation

Domain Model

class Speaker { public function addPresentation($aPresentation) public function getPresentations() public function hasPresentation($aPresentation) } class Presentation { public function setSpeaker($aSpeaker) public function getSpeaker() public function addTrack($aTrack) } class Track { }

Domain Model

class Speaker { public function addPresentation($aPresentation) public function getPresentations() public function hasPresentation($aPresentation) } class Presentation { public function addSpeaker($aSpeaker) public function getSpeakers() public function addTrack($aTrack) } class Track { }

Domain Model

class Presentation { public function addSpeaker($aSpeaker) public function getSpeakers() public function addTrack($aTrack) } class Track { public function addPresentation($aPresentation) }

Domain Model

class Presentation { public function addSpeaker($aSpeaker) public function getSpeakers() public function addTrack($aTrack) { $this->track = $aTrack; $aTrack->addPresentation($this); } } class Track { public function addPresentation($aPresentation) }

Domain Model

class Speaker { public function addPresentation($aPresentation) public function getPresentations() public function hasPresentation($aPresentation) public function startSpeaking() } class Presentation { public function setSpeaker($aSpeaker) public function getSpeaker() public function addTrack($aTrack) public function startPresentation($aTime) public function endPresentation($aTime) }

Front Controller

Central entry point

Map URL to command

multiple Front Controllers:

Debug

Test

Production

Alternative: Page Controller

Front Controller

class FrontController { public function __construct(RequestHelper $aRequestHelper) { $this->requestHelper = $aRequestHelper; } public function execute() { $cmd = $this->requestHelper->get('command'); $command = $this->mapCommand($cmd); print $command->execute(); } }

Front Controller

class FrontController { public function __construct(RequestHelper $aRequestHelper) { $this->requestHelper = $aRequestHelper; $this->commandMap = new CommandMap(); } protected function mapCommand($aCommand) { return $this->commandMap->mapCommand($aCommand); } }

Command Map

class CommandMap { protected $map = array('login' => 'LoginCommand'); public function mapCommand($aCommand) { if (!isset($this->map[$aCommand])) return new NoCommand(); return new $this->map[$aCommand]; } }

Initializing the Application

class FrontController { protected function initApplication() public function execute() { $this->initApplication(); ... } }

Applying Filters

class FrontController { protected $filters = array(); public function addFilter(Filter $aFilter) public function execute() { ... $result = $command->execute(); foreach($this->filters as $filter) { $result = $filter->filter($result); } print $result; } }

Data Mapper

Transfers data between database and domain objects

Separate relational mapping from domain objects

Decouple domain objects from database

Data Mapper

class SpeakerMapper { public static function load($aId) { ... $speaker = new Speaker($aId); $speaker->setValues(...); return $speaker; } public static function findByLastname($aName) protected function insert($aSpeaker) protected function update($aSpeaker) protected function delete($aId) }

Literature