Strange foreach loop after modifying array

Question

As I wrote some code, PHP confused me a little as I didn't expected the result of the following code:

$data = array(array('test' => 'one'), array('test' => 'two'));

foreach($data as &$entry) {
    $entry['test'] .= '+';
}

foreach($data as $entry) {
    echo $entry['test']."\n";
}

I think it should output

one+
two+

However the result is: http://ideone.com/e5tCsi

one+
one+

Can anyone explain to me why?

Answer 1

This is expected behaviour, see also https://bugs.php.net/bug.php?id=29992 .

The reference is maintained when using the second foreach, so when using the second foreach the value of $entry , which points still to $data[1] , is overwritten with the first value.

Ps (thanks to @billyonecan for saying it): you need to unset($entry) first, so that your reference is destroyed.

Answer 2

This is mentioned specifically in the documentation for foreach . You should unset the loop variable when it gets elements of the array by reference.

Warning

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