在 PHP 中創(chuàng)建對(duì)象需先定義類，再用 new 關(guān)鍵字實(shí)例化。1. 類是對(duì)象的藍(lán)圖，定義屬性和方法；2. 使用 new 創(chuàng)建對(duì)象實(shí)例；3. 構(gòu)造函數(shù)用于初始化不同數(shù)據(jù)；4. 通過(guò) -> 訪問(wèn)屬性和方法；5. 注意 public、private、protected 的訪問(wèn)控制；6. 可創(chuàng)建多個(gè)獨(dú)立實(shí)例，各自維護(hù)狀態(tài)。例如定義 Car 類后，new Car('red') 創(chuàng)建對(duì)象并傳參，$myCar->startEngine() 調(diào)用方法，每個(gè)對(duì)象互不影響。掌握這些有助于構(gòu)建更清晰、可擴(kuò)展的應(yīng)用程序。

In PHP, creating objects from classes is straightforward once you understand the basics of object-oriented programming (OOP). You define a class, then instantiate it using the new keyword. That’s how you get an object.

Understanding Classes and Objects

A class in PHP is like a blueprint — it defines properties and methods that an object will have. An object is an instance of a class. Think of a class as a recipe and the object as the actual dish made from that recipe.

Here's a basic example:

class Car {
    public $color = 'red';

    public function startEngine() {
        echo "Engine started!";
    }
}

To create an object from this class:

$myCar = new Car();

Now $myCar is an object based on the Car class and has access to its properties and methods.

Using Constructors for Custom Setup

Most of the time, you won’t want every object to be exactly the same. That’s where constructors come in handy. A constructor is a special method that runs when you create an object. It lets you pass values during instantiation.

Let’s update our Car class:

class Car {
    public $color;

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

    public function describe() {
        echo "This car is $this->color.";
    }
}

Now when you create a car, you can specify the color:

$redCar = new Car('red');
$blueCar = new Car('blue');

$redCar->describe();  // Outputs: This car is red.
$blueCar->describe(); // Outputs: This car is blue.

This way, each object can have different data while sharing the same structure.

Accessing Properties and Methods

Once an object is created, accessing its properties and methods is simple:

• Use -> to access properties or call methods.

For example:

echo $myCar->color;         // Access property
$myCar->startEngine();      // Call method

Be mindful of visibility:

• public means accessible from anywhere.
• private means only accessible within the class itself.
• protected means accessible within the class and any subclasses.

Visibility affects what you can do with the object outside of the class definition.

Creating Multiple Instances

You can create as many instances of a class as you need. Each one is separate from the others.

$car1 = new Car('black');
$car2 = new Car('white');

$car1->describe(); // This car is black.
$car2->describe(); // This car is white.

Each object maintains its own state. Changing one doesn’t affect the others.

Creating objects in PHP isn’t complicated, but knowing how to work with them effectively opens the door to building more organized and scalable applications.基本上就這些。

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