php 如何深度复制 DateTime 对象？
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How do I deep copy a DateTime object?
提问by Billy ONeal
$date1 = $date2 = new DateTime();
$date2->add(new DateInterval('P3Y'));
Now $date1and $date2contain the same date -- three years from now. I'd like to create two separate datetimes, one which is parsed from a string and one with three years added to it. Currently I've hacked it up like this:
现在$date1和$date2包含相同的日期 - 从现在起三年。我想创建两个单独的日期时间，一个是从字符串中解析出来的，另一个是添加了三年的时间。目前我已经破解了它：
$date2 = new DateTime($date1->format(DateTime::ISO8601));
but that seems like a horrendous hack. Is there a "correct" way to deep copy a DateTime object?
但这似乎是一个可怕的黑客攻击。是否有一种“正确”的方式来深度复制 DateTime 对象？
回答by Amy B
$date1 = new DateTime();
$date2 = new DateTime();
$date2->add(new DateInterval('P3Y'));
Update:
更新：
If you want to copy rather than reference an existing DT object, use clone, not =.
如果要复制而不是引用现有 DT 对象，请使用clone，而不是=。
$a = clone $b;
$a = clone $b;
回答by rjmunro
Clone the date with the cloneoperator:
使用克隆运算符克隆日期：
$date1 = new DateTime();
$date2 = clone $date1;
$date2->add(new DateInterval('P3Y'));
Clones are shallow by default, but deep enough for a DateTime. In your own objects, you can define the __clone()magic method to clone the properties (i.e. child objects) that make sense to be cloned when the parent object changes.
默认情况下，克隆是浅的，但对于 DateTime 来说足够深。在您自己的对象中，您可以定义__clone()魔术方法来克隆当父对象更改时克隆有意义的属性（即子对象）。
(I'm not sure why the documentation thinks a good example of needing to clone an object is GTK. Who uses GTK in PHP?)
（我不确定为什么文档认为需要克隆对象的一个很好的例子是 GTK。谁在 PHP 中使用 GTK？）
回答by Alexander Garden
PHP 5.5.0 introduced DateTimeImmutable. addand modifymethods of this class return new objects.
PHP 5.5.0 引入了DateTimeImmutable。此类的添加和修改方法返回新对象。
$date1 = new DateTimeImmutable();
$date2 = $date1->add(new DateInterval('P3Y'));
回答by jave.web
TLDR:
域名注册地址：
$date1 = new DateTime();
$date2 = (clone $date1)->modify('+3 years');
(Shallow copy is enaugh - Deep copy-ing DateTime makes (currently) nosense)
（浅拷贝就够了 -深拷贝 DateTime 使得（当前）没有意义）
Simple as that :)
就那么简单 ：）
Explanation "php create datetime object from another datetime":
解释“php从另一个日期时间创建日期时间对象”：
- The
clonekeyword makes regular shallowcopy - enaugh for this case (why => see below) - Wraping it with
()evaluates the expression returning the newly created object byclone ->modify()is therefore called on and modifies the new objectDateTime::modify(...)docs:Returns the DateTime object for method chaining or FALSE on failure.
$date2now contains the newly created & modified clone/copy, while$date1remains unchanged
- 该
clone关键字使常规浅拷贝- enaugh此情况下（为什么=>见下文） - 用它包装它
()评估返回新创建对象的表达式clone ->modify()因此被调用并修改新对象DateTime::modify(...)文档：返回用于方法链的 DateTime 对象，或者在失败时返回 FALSE。
$date2现在包含新创建和修改的克隆/副本，而$date1保持不变
Why you don't need to deepcopy here:
为什么你不需要在这里深拷贝：
Deep copy/clone is only necessary, when you need to copy targets of properties that are references, but this:
仅当您需要复制引用属性的目标时，才需要深度复制/克隆，但是：
class TestDateTime extends DateTime{
public function test(){
//*this* way also outputs private variables if any...
var_dump( get_object_vars($this) );
}
}
$test = (new TestDateTime())->test();
outputs:
输出：
array(3) {
["date"]=>
string(26) "2019-08-21 11:38:48.760390"
["timezone_type"]=>
int(3)
["timezone"]=>
string(3) "UTC"
}
so there are no references, just simple types => no need to deepcopy.
所以没有引用，只有简单的类型 => 不需要深复制。
回答by Hossein Shahdoost
You should change your DateTimeto DateTimeImmutable
你应该改变你DateTime的DateTimeImmutable
// from date time
$date = \DateTimeImmutable::createFromMutable($mutableDate)
then you can call any method on the DateTimewithout worrying about it change
然后你可以调用任何方法DateTime而不必担心它会改变
