php - 我应该在我的 php 项目中使用 `DateTimeInterface` 吗？

Question

最近，我发现有一个DateTimeInterface .当我使用 \DateTime 和 \DateTimeImmutable 时，我认为输入提示会很好。

然而在 php.net 上的变更日志上它说从 5.5.8 开始:

Trying to implement DateTimeInterface raises a fatal error now. Formerly implementing the interface didn't raise an error, but the behavior was erroneous.

上面写着我永远无法实现我自己的 CustomDateTime 类来实现 DateTimeInterface，这看起来很奇怪。

我应该在用户空间代码中使用 DateTimeInterface 吗？

我的直觉告诉我不要这样做。然而，对对象进行类型提示也是不对的，即

@var \DateTime|\DateTimeImmutable|\MyCustomDateTime

Answer 1

当您期望任何一种 native DateTime 变体时，您可以使用 DateTimeInterface 类型提示，例如\DateTime 或 \DateTimeImmutable。

但正如文档所说

It is not possible to implement this interface with userland classes.

因此，如果您计划使用您自己的实现来实现 \DateTimeInterface，这将不起作用，例如

class MyDateTime implements \DateTimeInterface {} // will raise an error

但是，您可以创建自己的界面并改编 native DateTime 类。

interface MyDateTime { /* some methods */ }

class NativeDateTime implements MyDateTime 
{
    private $dateTime;

    public function __construct($args = 'now') {
        $this->dateTime = new \DateTimeImmutable($args);
    }

   /* some methods */
}

或者您可以扩展 native DateTime 变体，然后显然会实现 DateTimeInterface，例如

class MyDateTime extends \DateTimeImmutable 
{
    /* your modifications */
}

var_dump(new MyDateTime instanceof \DateTimeInterface); // true

详细说明为什么您不能实现自己的实现 \DateTimeInterface 的类:

• https://github.com/php/php-src/pull/512
• https://www.mail-archive.com/internals@lists.php.net/msg79534.html

tl;dr core functions that accept DateTime and DateTimeImmutable (DateTimeInterface basically) operate directly on timelib structures hence they will break if you pass them a user-defined class. There's a workaround though - it's to always call user-defined class's method directly from built-in functions, so if you would call (new DateTime())->diff(new UserDefinedDateTime()) it would call UserDefinedDateTime#diff in the end which would need to implement the logic.