Unexpected behavior of arrays with referenced elements, in PHP

references-and-arrays.php

<?php

$arr = array(1, 5);
$a =& $arr[0]; //$a and $arr[0] are in the same reference set
$arr2 = $arr; //not an assignment-by-reference!
$arr2[0]++;
$arr2[1]++;

var_dump($a);
var_dump($arr);

// Result is unexpected:
// int(2) array(2) { [0]=> &int(2) [1]=> int(5) }