Be careful with iterating arrays by reference

I just stumbled upon a very unpleasant PHP feature when iterating through arrays with reference to elements (foreach construction with &).

See for yourself:

$test = array('1' => 1, '2' => 2, '3' => 3, '4' => 4, '5' => 5);
print_r($test);
foreach ($test as $key => $value) {
	echo"{$key} => {$value}\n";
}

We get what we expected:

Array
(
    [1] => 1
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 5
)
1 => 12 => 23 => 34 => 45 => 5

But it’s worth adding an iteration by reference:

$test = array('1' => 1, '2' => 2, '3' => 3, '4' => 4, '5' => 5);
foreach ($test AS &$value) {
	// какие-то действия. Но для теста и пустого цикла достаточно
}
print_r($test);
foreach ($test as $key => $value) {
	echo"{$key} => {$value}\n";
}

... how to get an unexpected result:

Array
(
    [1] => 1
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 5
)
1 => 12 => 23 => 34 => 45 => <b>4</b>

I do not fully understand what the jamb is, it is somehow connected with the fact that in $ value there is a link to the last element after exiting the first loop. There are two ways to avoid this behavior: Either you need to iterate the second loop by reference too, or use a different name instead of $ value.

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Be careful with iterating arrays by reference

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