为什么PHP私有变量在扩展类上起作用? [英] Why is PHP private variables working on extended class?
问题描述
当我尝试从扩展类而不是基类中设置属性的值时，它是否会生成错误?
Shouldn't it generate error when i try to set the value of a property from the extended class instead of a base class?
<?php
class first{
public $id = 22;
private $name;
protected $email;
public function __construct(){
echo "Base function constructor<br />";
}
public function printit(){
echo "Hello World<br />";
}
public function __destruct(){
echo "Base function destructor!<br />";
}
}
class second extends first{
public function __construct($myName, $myEmail){
$this->name = $myName;
$this->email = $myEmail;
$this->reveal();
}
public function reveal(){
echo $this->name.'<br />';
echo $this->email.'<br />';
}
}
$object = new second('sth','aaa@bbb.com');
?>
推荐答案
私有变量在子类中不可访问.这就是访问修饰符 protected 的用途.发生的事情是，当您访问一个不存在的变量时，它将使用默认的访问修饰符 public 为您创建一个变量.
Private variables are not accessible in subclasses. Thats what the access modifier protected is for. What happened here is that when you access a variable that doesn't exist, it creates one for you with the default access modifier of public.
这是向您显示状态的UML:
Here is the UML to show you the state:
请注意:子类仍然可以访问其父类中的所有 public 和 protected 方法和变量-但不在UML图中！
Please note: the subclass still has access to all the public and protected methods and variables from its superclass - but are not in the UML diagram!
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