PHP基础学习笔记（面向对象OOP）

类和对象

<?php
//声明一个名为 Fruit 的类，它包含两个属性（$name 和 $color）以及两个用于设置和获取 $name 属性的方法 set_name() 和 get_name()：
class Fruit {// Propertiespublic $name;public $color;// Methodsfunction set_name($name) {$this->name = $name;}function get_name() {return $this->name;}
}
?>

构造函数

构造函数允许您在创建对象时初始化对象的属性。

<?php
class Fruit {public $name;public $color;function __construct($name) {$this->name = $name;}function get_name() {return $this->name;}
}$apple = new Fruit("Apple");
echo $apple->get_name(); //Apple
$orange = new Fruit("Orange");
echo $orange->get_name();
?>

析构函数

当对象被破坏或脚本停止或退出时，会调用一个析构函数。
如果你创建了一个__destruct()函数，PHP会在脚本结束时自动调用这个函数。

<?php
class Fruit {public $name;public $color;function __construct($name) {$this->name = $name;}function __destruct() {echo "The fruit is {$this->name}.";}
}$apple = new Fruit("Apple"); //The fruit is Apple.
?>

<?php
class Fruit {public $name;public $color;function __construct($name, $color) {$this->name = $name;$this->color = $color;}function __destruct() {echo "The fruit is {$this->name} and the color is {$this->color}.";}
}$apple = new Fruit("Apple", "red"); //The fruit is Apple and the color is red.?>

访问修饰符

属性和方法可以有访问修饰符来控制它们的访问位置。

/*
有三种访问修饰符：public - 可以从任何地方访问属性或方法。 这是默认设置
protected - 属性或方法可以在类内以及从该类派生的类中访问
private - 属性或方法只能在类中访问
*/<?php
class Fruit {public $name;protected $color;private $weight;
}$mango = new Fruit();
$mango->name = 'Mango'; // OK
$mango->color = 'Yellow'; // ERROR
$mango->weight = '300'; // ERROR
?>

继承

子类将从父类继承所有公共和受保护的属性和方法。 此外，它还可以有自己的属性和方法。

<?php
class Fruit {public $name;public $color;public function __construct($name, $color) {$this->name = $name;$this->color = $color;}public function intro() {echo "The fruit is {$this->name} and the color is {$this->color}.";}
}// Strawberry is inherited from Fruit
class Strawberry extends Fruit {public function message() {echo "Am I a fruit or a berry? ";}
}
$strawberry = new Strawberry("Strawberry", "red");
$strawberry->message(); //Am I a fruit or a berry? 
$strawberry->intro(); //The fruit is Strawberry and the color is red.
?>