PHP Object-Oriented Programming: Practical Exercise

PHP Object-oriented programming (OOP) is a programming paradigm that simulates real entities. The core concepts of OOP include: Classes and Objects: A class defines a blueprint for an object, and an object is an instance of a class. Encapsulation: Object properties and methods are isolated from other code. Inheritance: Subclasses can inherit the properties and methods of the parent class. Polymorphism: A method with the same name exhibits different behavior at runtime depending on the type of object.

PHP Object-Oriented Programming: Practical Exercise

Introduction

Object-Oriented Programming (OOP) is a widely adopted programming paradigm in modern software development that is based on the idea of ​​modeling real-world entities. In this article, we will explore OOP in PHP in depth and demonstrate its power through practical examples.

Classes and Objects

In OOP, a class is the blueprint of an object, which defines its data and behavior. An object is an instance of a class that has its own data and behavior, but the behavior is governed by the definition of the class to which it belongs.

Code sample:

class Car {
  private $model;
  private $make;

  public function __construct($model, $make) {
    $this->model = $model;
    $this->make = $make;
  }

  public function getDetails() {
    return "Model: {$this->model}, Make: {$this->make}";
  }
}

$car = new Car('Camry', 'Toyota');
echo $car->getDetails();

Encapsulation

Encapsulation is one of the core principles of OOP, which describes how to The ability of an object's properties and methods to be isolated from other code.

Code Example:

class User {
  private $username;
  private $password;

  public function setUsername($username) {
    // 验证用户名并设置
    $this->username = $username;
  }

  public function getUsername() {
    return $this->username;
  }
}

$user = new User();
$user->setUsername('admin');
echo $user->getUsername();

Inheritance

Inheritance allows the creation of a new class ( Subclass), the new class will inherit the data and behavior of the parent class, and can also define its own specific properties and methods.

Code example:

class Vehicle {
  private $make;
  private $model;

  public function __construct($make, $model) {
    $this->make = $make;
    $this->model = $model;
  }

  public function getDetails() {
    return "Make: {$this->make}, Model: {$this->model}";
  }
}

class Car extends Vehicle {
  private $numWheels;

  public function __construct($make, $model, $numWheels) {
    parent::__construct($make, $model);
    $this->numWheels = $numWheels;
  }

  public function getDetails() {
    return parent::getDetails() . ", Num Wheels: {$this->numWheels}";
  }
}

$car = new Car('Toyota', 'Camry', 4);
echo $car->getDetails();

Polymorphism

Polymorphism allows parent and child class methods to have the same name, but exhibits different behavior at runtime depending on the actual type of the object.

Code example:

class Polygon {
  abstract public function getArea();
}

class Rectangle extends Polygon {
  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 extends Polygon {
  private $radius;

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

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

function calculateTotalArea($polygons) {
  $totalArea = 0;
  foreach ($polygons as $polygon) {
    $totalArea += $polygon->getArea();
  }
  return $totalArea;
}

$polygons = [
  new Rectangle(5, 10),
  new Circle(5),
];

echo calculateTotalArea($polygons);

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