In-depth understanding of PHP object-oriented programming: interaction between classes and objects

Object-oriented programming (OOP) is a programming paradigm that encapsulates data and behavior in objects to represent real-world entities. In PHP, OOP allows the creation of classes and objects to represent entities in the real world: Classes: Define the data (properties) and operations (methods) of an object. Object: An instance of a class that contains the properties and methods of that class and can interact with other objects. OOP practical example: A shopping cart contains a series of products, modeled by the following two classes: Product: Represents a single product, with a name and price. Cart: Represents a shopping cart, containing a list of products and providing methods for adding products and calculating the total price.

PHP In-depth understanding of object-oriented programming: interaction between classes and objects

What is object-oriented programming?

Object-oriented programming (OOP) is a programming paradigm that encapsulates data and behavior in objects. In PHP, OOP allows us to create classes and objects to represent entities in the real world.

Classes and Objects

• Class: A class is a blueprint for a group of objects with common characteristics and behaviors. It defines the object's data (properties) and operations (methods).
• Object: An object is an instance of a class. It contains the properties and methods of the class and can interact with other objects.

Class definition

class Person {
  private $name;
  private $age;

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

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

  public function setName($name) {
    $this->name = $name;
  }

  public function getAge() {
    return $this->age;
  }

  public function setAge($age) {
    $this->age = $age;
  }
}

Object creation

To create a human object, we can use The following code:

$person = new Person('John Doe', 30);

Accessing properties and methods

We can use the -> operator to access the properties and methods of an object:

echo $person->getName(); // 输出："John Doe"

$person->setAge(35);

Practical Case: Shopping Cart

Consider an example of a shopping cart that contains a list of products:

class Product {
  private $name;
  private $price;

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

  // ...
}

class Cart {
  private $products = [];

  public function addProduct(Product $product) {
    $this->products[] = $product;
  }

  public function getTotalPrice() {
    $totalPrice = 0;
    foreach ($this->products as $product) {
      $totalPrice += $product->getPrice();
    }

    return $totalPrice;
  }

  // ...
}

We can use these classes to create a shopping cart And add products:

$cart = new Cart();
$product1 = new Product('Apple', 10);
$product2 = new Product('Orange', 5);

$cart->addProduct($product1);
$cart->addProduct($product2);

echo $cart->getTotalPrice(); // 输出："15"

This object-oriented approach allows us to create reusable and maintainable programs to represent and manipulate data and behavior in real-world scenarios.

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