PHP classes and objects: learn object-oriented programming from scratch in simple terms

PHP classes and objects are the basis of object-oriented programming, which may be difficult for beginners to understand. In this guide, PHP editor Banana will start from scratch and introduce the concepts and basic principles of PHP classes and objects in a simple and easy-to-understand manner to help readers easily understand the important concepts of object-oriented programming. Whether you are a newbie or an experienced developer, this article will provide you with helpful guidance and help you better master the knowledge of PHP classes and objects.

In PHP, a class is the template of an object, which defines the structure of the object's data and methods. An object is an instance of a class. It is created according to the template of the class and has all the data and methods of the class.

To create a class, you can use the class keyword, followed by the class name. The class name should start with a capital letter. In the definition of a class, you can control the visibility of data using the public, protected, and private keywords.

class MyClass {
public $public_data;
protected $protected_data;
private $private_data;

public function __construct($public_data, $protected_data, $private_data) {
$this->public_data = $public_data;
$this->protected_data = $protected_data;
$this->private_data = $private_data;
}

public function publicMethod() {
echo "This is a public method.
";
}

protected function protectedMethod() {
echo "This is a protected method.
";
}

private function privateMethod() {
echo "This is a private method.
";
}
}

To create an object, you can use the new keyword, followed by the class name.

$myObject = new MyClass("public data", "protected data", "private data");

To access an object's data and methods, you can use the object's arrow notation (->).

echo $myObject->public_data; // 输出：public data
$myObject->publicMethod(); // 输出：This is a public method.

To call a protected method of an object, you can use the parent:: operator.

class ChildClass extends MyClass {
public function callProtectedMethod() {
parent::protectedMethod(); // 输出：This is a protected method.
}
}

$childObject = new ChildClass();
$childObject->callProtectedMethod(); // 输出：This is a protected method.

To call the private method of an object, you can use the self:: operator.

class MyClass {
private function privateMethod() {
echo "This is a private method.
";
}

public function callPrivateMethod() {
self::privateMethod(); // 输出：This is a private method.
}
}

$myObject = new MyClass();
$myObject->callPrivateMethod(); // 输出：This is a private method.

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