PHP 类型提示与接口和抽象类不符? [英] Php type hinting not getting along with interfaces and abstract classes?

问题描述

我认为在代码示例中看到问题比首先编写问题要容易得多.这是我的php代码:

I think it'll be much easier to see the problem in a code example than writing the question in the first place. Here is my php code:

<?php

interface AnInterface
{
        public function method();
}    

class AClass implements AnInterface
{
        public function method()
        {
                echo __METHOD__;
        }
}    

abstract class AnAbstractClass
{
        abstract public function method( AnInterface $Object );
}

class ConcreteClass extends AnAbstractClass
{
        public function method( AClass $Object )
        {
                $Object->method();
        }
}

$Object1 = new ConcreteClass();
$Object2 = new AClass();

$Object1->method( $Object2 );

以上代码导致如下错误:

The above code causes the following error:

致命错误:ConcreteClass::method() 的声明必须与 AnAbstractClass::method() 的声明兼容

Fatal error: Declaration of ConcreteClass::method() must be compatible with that of AnAbstractClass::method()

问题是 php 似乎没有将 AnAbstractClass::method 和 ConcreteClass::method 的签名识别为兼容.难道我做错了什么?谢谢！

The problem is that php doesn't seem to be recognizing the signatures of AnAbstractClass::method and ConcreteClass::method as compatible. Am I doing something wrong? Thanks!

推荐答案

php 似乎无法将 AnAbstractClass::method 和 ConcreteClass::method 的签名识别为兼容.

php doesn't seem to be recognizing the signatures of AnAbstractClass::method and ConcreteClass::method as compatible.

PHP 是正确的，它们不兼容.通过仅允许将 AClass(或其子项)的实例传递给 ConcreteClass::method，您违反了 AnAbstractClass 提供的契约:它的任何子类都必须接受 AnInterface 作为其 method() 的参数.

PHP is correct, they're not compatible. By allowing only instances of AClass (or its children) to be passed to ConcreteClass::method, you're breaking the contract that AnAbstractClass provides: Any of its subclasses must accept AnInterface as an argument to its method().

如果您的示例有效，并且我有另一个类 BClass 实现了 AnInterface，我们将遇到一种情况，根据 AnAbstractClass，method() 应该接受 BClass 的实例，而根据 ConcreteClass，它不应该.

If your example worked, and I had another class BClass implementing AnInterface, we'd have a situation where according to AnAbstractClass, method() should accept instances of BClass, while according to ConcreteClass, it shouldn't.

更改ConcreteClass::method 的签名以匹配AnAbstractClass::method 的签名.

Change your signature for ConcreteClass::method to match that of AnAbstractClass::method.

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