1. 继承和多态 继承是面向对象编程中的一种重要机制,它允许一个类从另一个类继承属性和方法。继承分为单继承和多重继承,单继承是指一个类只能从一个父类继承,而多重继承是指一个类可以从多个父类继承。
class ParentClass {
public function __construct() {
echo "Parent class constructor called
";
}
public function sayHello() {
echo "Hello from parent class
";
}
}
class ChildClass extends ParentClass {
public function __construct() {
parent::__construct();
echo "Child class constructor called
";
}
public function sayHello() {
echo "Hello from child class
";
}
}
$child = new ChildClass();
$child->sayHello();
2. 接口和抽象类 接口是 PHP 中用于定义方法签名的特殊类。接口中的方法都是抽象的,即没有具体实现。要实现接口,类必须实现接口中定义的所有方法。
interface Vehicle {
public function drive();
public function brake();
}
class Car implements Vehicle {
public function drive() {
echo "Car is driving
";
}
public function brake() {
echo "Car is braking
";
}
}
class Bike implements Vehicle {
public function drive() {
echo "Bike is riding
";
}
public function brake() {
echo "Bike is braking
";
}
}
$car = new Car();
$car->drive(); // Output: Car is driving
$car->brake(); // Output: Car is braking
$bike = new Bike();
$bike->drive(); // Output: Bike is riding
$bike->brake(); // Output: Bike is braking
3. 封装、可见性和访问控制 封装是面向对象编程中的一种重要概念,它指将数据的实现细节隐藏起来,只暴露公共接口。在 PHP 中,封装可以通过访问控制关键字来实现,包括 public、protected 和 private。
class MyClass {
private $name;
public function setName($name) {
$this->name = $name;
}
public function getName() {
return $this->name;
}
}
$obj = new MyClass();
$obj->setName("John Doe");
echo $obj->getName(); // Output: John Doe
4. 类常量和静态属性 类常量和静态属性是属于类本身,而不是类实例的属性和方法。类常量是使用 const 关键字定义的,而静态属性是使用 static 关键字定义的。
class MyClass {
const NAME = "John Doe";
public static $age = 30;
public function sayHello() {
echo "Hello, my name is " . self::NAME . " and I am " . self::$age . " years old
";
}
}
MyClass::sayHello(); // Output: Hello, my name is John Doe and I am 30 years old
5. 魔术方法和魔术常量 魔术方法是 PHP 中的一组预定义方法,当某些事件发生时自动调用。魔术常量则是一些预定义的常量,可以用于获取有关类或对象的信息。
class MyClass {
public function __construct() {
echo "Constructor called
";
}
public function __destruct() {
echo "Destructor called
";
}
public function __toString() {
return "This is an instance of MyClass
";
}
}
$obj = new MyClass();
echo $obj; // Output: This is an instance of MyClass
unset($obj); // Output: Destructor called
结论: 深入理解 PHP 类与对象的高级技巧,可以帮助您编写出更加健壮、灵活和可维护的代码。通过掌握继承、多态、封装、可见性控制、类常量、静态属性、魔术方法和魔术常量等高级概念,您可以将面向对象编程的优势发挥到极致,构建出更加复杂和强大的应用程序。