PHP foreach by reference 在遍历对象数组时会导致奇怪的故障

2021-12-26 00:00:00 foreach php

我有一个对象数组.对象主要有一堆属性，因为这些是元数据对象.

I have an array of objects. The objects mainly have a bunch of properties because these are meta-data objects.

所以就像$objects[] 就像一堆具有以下属性的项目:object->item1、object->item2等

so it is like $objects[] is like a bunch of items that have properties like: object->item1, object->item2, etc.

我想为每个对象添加一些东西，所以...

I want to add something to each of these objects, so...

foreach ($objects as &$object) {
  $object->newItem=(something I compute);
}

然后，我想将这些对象显示为 html 中的列表.所以，我去:

then later, I want to display these objects as a list in html. So, I go:

foreach ($objects as $object) {
  <li><?php object output stuff here ?></li>
}

好的.现在，它工作正常，除了最后一个对象被丢弃并且倒数第二个对象显示两次.跆拳道??

ok. Now, it works fine, except the last object is discarded and the second to last object is displayed twice. WTF??

这对你有意义吗?

推荐答案

如果你通过引用迭代，之后总是取消设置迭代变量:

If you iterate by reference, always unset the iteration variable afterwards:

foreach ($objects as &$object) {
      // some code
}
unset($object);

摘自 foreach 文档:

Excerpt from the foreach documentation:

即使在 foreach 循环之后，对 $value 和最后一个数组元素的引用仍然存在.建议用unset()销毁.

Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset().

如果您想了解为什么您的代码的行为方式如此，这里有一些进一步的阅读:引用和foreach

If you want to understand why your code behaves the way it behaves, here is some further reading: References and foreach

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