基类不允许访问私有成员? [英] Base class not permitted to access private member?

问题描述

我可以发誓，在标准 OOP 中，您可以从基类中的方法访问具体类的私有成员.PHP 只是以不同的方式实现这一点，还是我做错了什么，或者我的理解完全错误?

I could have sworn that in standard OOP, you can access the private members of the concrete class from a method in the base class. Does PHP just implement this differently, or am I doing something wrong, or was my understanding entirely wrong?

<?php

class Base {
  public function __toString() {
    return $this->name;
  }
}

class Concrete extends Base {
  private $name;

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

$o = new Concrete('foobar');
echo $o;

上面的代码片段抛出致命错误:无法访问第 5 行的私有属性 Concrete::$name.如果我将 $name 的访问级别更改为 protected，它会起作用.

The above code fragment throws Fatal error: Cannot access private property Concrete::$name on line 5. It works if I change the access level of $name to protected.

演示

推荐答案

private 通常意味着它只能从类内部访问.我认为这是预期的行为.

private usually means that it can be accessed ONLY from within the class. I think this is expected behaviour.

来自 PHP 文档:

属性或方法的可见性可以通过在声明前加上关键字 public、protected 或 private 来定义.声明为 public 的类成员可以在任何地方访问.声明为 protected 的成员只能在类本身内以及被继承类和父类访问.声明为私有的成员只能由定义该成员的类访问.

The visibility of a property or method can be defined by prefixing the declaration with the keywords public, protected or private. Class members declared public can be accessed everywhere. Members declared protected can be accessed only within the class itself and by inherited and parent classes. Members declared as private may only be accessed by the class that defines the member.

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