This code is causing unexpected array content change. What could be the reason of this:
<?php
$arr[] = array('a', 'b');
$arr[] = array('c', 'd');
print_r($arr);
foreach ($arr as &$processed_arr) {
}
foreach ($arr as $processed_arr) {
}
print_r($arr);
Output:
Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )
    [1] => Array
        (
            [0] => c
            [1] => d
        )
)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )
    [1] => Array
        (
            [0] => a
            [1] => b
        )
)
 
    