PHP foreach by reference causes weird glitch when going through array of objects

Question

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

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

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

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

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>
}

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

Does this make sense to you?

duplicate of stackoverflow.com/q/3307409

qdinar
– qdinar

2017-06-09 13:29:06 +00:00
Commented Jun 9, 2017 at 13:29 — qdinar
– qdinar, Commented Jun 9, 2017 at 13:29

NikiC · Accepted Answer · 2011-04-27 20:32:06Z

39

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

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

Excerpt from the foreach documentation:

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

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

answered Apr 27, 2011 at 20:32

NikiC

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6 Comments

prodigitalson Over a year ago

+1 for answering the question, but he doesnt really need to loop by reference since he is working with objects... does he?

NikiC Over a year ago

@prodigitalson: Yep, you're right. ^^ I'm always thinking too comlicated

prodigitalson Over a year ago

haha.. it happens (to me more often than id liek to admit). you did answer the question though which is important when one does need to loop by reference.

Brenn Over a year ago

Thank you! I was tearing my hair out about this. I actually wrote a workaround in the meantime, but I've come across this weirdness a few times and never understood it. GREAT link BTW.

NikiC Over a year ago

@Brenn: If this answer answers your question, you should accept it, by clicking on the green tick next to it :)

|

HappyDeveloper · Accepted Answer · 2012-07-07 23:51:39Z

4

Objects are always references, so just remove the '&'

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

foreach ($objects as $object) {
  echo "<li>{$object->someResult()}</li>";
}

I know you already got your answer, but this might help other devs find it faster.

edited Jul 7, 2012 at 23:51

answered Jul 7, 2012 at 23:46

HappyDeveloper

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