'PHP 物件導向程式設計模式：理解 SOLID 原則及其應用”

PHP 物件導向程式設計模式一直是開發者研究的熱門話題。在這篇文章中，php小編草莓將深入探討SOLID原則，幫助讀者理解並應用這些設計原則。 SOLID原則是物件導向程式設計中的基石，包括單一職責原則、開放封閉原則、里氏替換原則、介面隔離原則和依賴倒置原則。透過學習和實踐這些原則，開發者可以寫出更靈活、可維護和可擴展的PHP程式碼。

1. 單一職責原則（Single Responsibility Principle，SRP）：一個類別應該只負責一項任務，並且這個任務應該被封裝在類別中。這樣可以提高類別的可維護性和可重複使用性。

class User {
private $id;
private $name;
private $email;

public function __construct($id, $name, $email) {
$this->id = $id;
$this->name = $name;
$this->email = $email;
}

public function getId() {
return $this->id;
}

public function getName() {
return $this->name;
}

public function getEmail() {
return $this->email;
}
}

class UserRepository {
private $connection;

public function __construct($connection) {
$this->connection = $connection;
}

public function save(User $user) {
$stmt = $this->connection->prepare("INSERT INTO users (name, email) VALUES (?, ?)");
$stmt->execute([$user->getName(), $user->getEmail()]);
}

public function find($id) {
$stmt = $this->connection->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$id]);
$result = $stmt->fetch();

if ($result) {
return new User($result["id"], $result["name"], $result["email"]);
}

return null;
}
}

2. 開放-封閉原則（Open-Closed Principle，OCP）：軟體實體（類別、模組等）應該對擴充開放，對修改關閉。這樣可以提高軟體的靈活性，並降低軟體維護成本。

interface Shape {
public function getArea();
}

class Rectangle implements Shape {
private $width;
private $height;

public function __construct($width, $height) {
$this->width = $width;
$this->height = $height;
}

public function getArea() {
return $this->width * $this->height;
}
}

class Circle implements Shape {
private $radius;

public function __construct($radius) {
$this->radius = $radius;
}

public function getArea() {
return pi() * $this->radius ** 2;
}
}

class ShapeCalculator {
public function calculateTotalArea($shapes) {
$totalArea = 0;
foreach ($shapes as $shape) {
$totalArea += $shape->getArea();
}

return $totalArea;
}
}

3. 里氏替換原則（Liskov Substitution Principle，LSP）：子類別可以替換其父類別而不會影響程式的正確性。這樣可以提高軟體的靈活性，讓軟體更容易重構。

class Animal {
public function eat() {
echo "Animal is eating.";
}
}

class Dog extends Animal {
public function bark() {
echo "Dog is barking.";
}
}

class Cat extends Animal {
public function meow() {
echo "Cat is meowing.";
}
}

function feedAnimal(Animal $animal) {
$animal->eat();
}

feedAnimal(new Dog()); // prints "Dog is eating."
feedAnimal(new Cat()); // prints "Cat is eating."

4. 介面隔離原則（Interface Segregation Principle，ISP）：應該使用多個專門的接口，而不是一個通用的接口。這樣可以提高軟體的可讀性，並降低軟體維護成本。

interface Printable {
public function print();
}

interface Scannable {
public function scan();
}

interface Faxable {
public function fax();
}

class Printer implements Printable {
public function print() {
echo "Printer is printing.";
}
}

class Scanner implements Scannable {
public function scan() {
echo "Scanner is scanning.";
}
}

class FaxMachine implements Faxable {
public function fax() {
echo "Fax machine is faxing.";
}
}

class MultifunctionDevice implements Printable, Scannable, Faxable {
public function print() {
echo "Multifunction device is printing.";
}

public function scan() {

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