Clean PHP

Clean PHPSebastian Bergmann May 20 th 2011

Hello! My name is Sebastian. Sebasti a n

Hello! My name is Sebastian …and this is what I do: sebastian@thePHP.cc Co-Founder of The PHP Consulting Company sebastian@phpunit.de Creator and Main Developer of PHPUnit sebastian@php.net Contributor to PHP sebastian@apache.org Contributor to Zeta Components sbergmann@{acm.org | ieee.org} Practitioner of academic computing

Source Code Conventions

Keep It Simple, Stupid (KISS)

Beware of optimizations

You Aint Gonna Need It (YAGNI)

Dont Repeat Yourself (DRY)

Principle of Least Astonishment

Information Hiding Principle

Liskov Substitution Principle

Separation of Concerns

Separation of ConcernsActive Record = Domain Logic + Row Data Gatewayclass User { protected $name; public function setName($name) { $this->name = $name; } public function getName() { return $this->name; } public function calculateRevenue() { // ... domain logic ... } public function insert() { /* ... */ } public function update() { /* ... */ } public function delete() { /* ... */ }}

Separation of ConcernsData Mapperclass User { protected $name; public function setName($name) { $this->name = $name; } public function getName() { return $this->name; } public function calculateRevenue() { // ... domain logic ... }}class UserMapper { public function findByName($name) { /* ... */ } public function insert(User $user) { /* ... */ } public function update(User $user) { /* ... */ } public function delete(User $user) { /* ... */ }}

Single Responsibility Principle

Open Closed Principle

Open Closed Principlepublic function price($price, $quantity, $customerType) { switch ($customerType) { case ONE_TIME_CUSTOMER: { return $quantity * $price; } case RETURNING_CUSTOMER: { return $quantity * $price * RETURNING_CUSTOMER_REBATE; } default: { throw new InvalidArgumentException; } }}

Open Closed Principleinterface PriceCalculator { public function price($quantity, $price);}class OneTimeCustomerPriceCalculator implements PriceCalculator { public function price($quantity, $price) { return $quantity * $price; }}class ReturningCustomerPriceCalculator implements PriceCalculator { const REBATE = 0.95; public function price($quantity, $price) { return $quantity * $price * self::REBATE; }}

Tell, Dont Ask

Law of Demeter

Favour composition over inheritance

Interface Segregation Principle

Dependency Injection

Dependency Injectionclass BankAccountController extends Controller { public function execute(Request $request, Response $response) { $mapper = new BankAccountMapper( /* … */ ); $ba = $mapper->findById($request->get(id)); $response->set(balance, $ba->getBalance()); return BankAccountView; }}

Dependency InjectionConstructor Injectionclass BankAccountController extends Controller { protected $mapper; public function __construct(BankAccountMapper $mapper) { $this->mapper = $mapper; } public function execute(Request $request, Response $response) { $ba = $this->mapper->findById($request->get(id)); $response->set(balance, $ba->getBalance()); return BankAccountView; }}

Dependency InjectionSetter Injectionclass BankAccountController extends Controller { protected $mapper; public function setMapper(BankAccountMapper $mapper) { $this->mapper = $mapper; } public function execute(Request $request, Response $response) { if ($this->mapper === NULL) { throw new LogicException; } $ba = $this->mapper->findById($request->get(id)); $response->set(balance, $ba->getBalance()); return BankAccountView; }}

Dependency InjectionIntermediate Solution: Optional Injectionclass BankAccountController extends Controller { protected $mapper; public function __construct(BankAccountMapper $mapper = NULL) { if ($mapper === NULL) { $mapper = new BankAccountMapper; } $this->mapper = $mapper; } public function execute(Request $request, Response $response) { $ba = $this->mapper->findById($request->get(id)); $response->set(balance, $ba->getBalance()); return BankAccountView; }}

Dependency InjectionIntermediate Solution: Dependency Lookupclass BankAccountController extends Controller { public function execute(Request $request, Response $response) { $mapper = Registry::getInstance() ->getObject(BankAccountMapper); $ba = $mapper->findById($request->get(id)); $response->set(balance, $ba->getBalance()); return BankAccountView; }}

Component-Oriented Development

The Boy Scout Rule

Refactoring

Refactoring Refactoring Improving the Design of Existing Code Martin Fowler Addison-Wesley, 1999

Reviews

Iterative Development

Automated Unit Tests

Automated Unit Tests<?phpclass BankAccountTest extends PHPUnit_Framework_TestCase{ public function testBalanceIsInitiallyZero() { $ba = new BankAccount; $this->assertEquals(0, $ba->getBalance()); }}

Code Coverage Analysis

Mock Objects

A class we want to test<?phpclass ClassUnderTest { private $dependency; public function __construct(Dependency $dependency) { $this->dependency = $dependency; } public function bar() { $value = $this->dependency->foo(); // … return $someOtherValue; }}

A dependency of the class we want to test<?phpclass ClassUnderTest { private $dependency; public function __construct(Dependency $dependency) { $this->dependency = $dependency; } public function bar() { $value = $this->dependency->foo(); // … return $someOtherValue; }}class Dependency { public function foo() { // … }}

A test for the class we want to test<?phpclass ClassUnderTestTest extends PHPUnit_Framework_TestCase { public function testBar() { $dependency = new Dependency; $object = new ClassUnderTest($dependency); // … $this->assertEquals(/* … */, $object->bar()); }}

A test for the class we want to testthat does not use the real dependency.<?phpclass ClassUnderTestTest extends PHPUnit_Framework_TestCase { public function testBar() { $dependency = new DependencyStub; $object = new ClassUnderTest($dependency); // … $this->assertEquals(/* … */, $object->bar()); }}class DependencyStub extends Dependency { public function foo() { return value; }}

A test for the class we want to test thatuses PHPUnit_MockObject for stubbing.<?phpclass ClassUnderTestTest extends PHPUnit_Framework_TestCase { public function testBar() { $dependency = $this->getMock(Dependency); $dependency->expects($this->any()) ->method(foo) ->will($this->returnValue(value)); $object = new ClassUnderTest($dependency); // … $this->assertEquals(/* … */, $object->bar()); }}

Test First

Software Metrics

SOLID Single Responsibility Principle Open / Closed Principle Liskov Substitution Principle Interface Segregation Principle Dependency Inversion Principle

Software Quality in PHP Projects Sebastian Bergmann Stefan Priebsch Wrox, May 2011

Clean Code Clean Code Robert C. Martin Prentice Hall, 2008

The End Web: http://thePHP.cc/ http://sebastian-bergmann.de/ Mail: sebastian@thePHP.cc Twitter: @s_bergmann Slides: http://talks.thePHP.cc/

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Clean PHP

by Sebastian Bergmann on May 20, 2011

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