Predict the output · PHP

foreach by Reference Leftover

Medium Predict the output Seen at Automattic, Mollie

What does this print?

<?php
$items = [1, 2, 3];
foreach ($items as &$item) {
}
foreach ($items as $item) {
}
echo implode(',', $items);

```
1,2,3
```
```
1,2,2
```
```
3,3,3
```
```
1,1,1
```

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Solution

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The output is:

1,2,2

After the first loop, $item is still a reference to the last element ($items[2]). The second loop assigns each element to $item — i.e. writes into $items[2]: it becomes 1, then 2, then (reading itself) stays 2.

Always unset($item) after a by-reference foreach, or avoid references and use array_map/keys.

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What does this print?

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Solution

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