Description:
------------
Affects both PHP 5.6.21 and PHP 7.0.6 .

- Create an array with some elements
- Iterate over this array by reference
- assign (copy) this array by value to a different variable
- Iterate over the previous array by reference again using the same variable
- the copied array changes at the value which was the last of the original one


Test script:
---------------
<?php
    $x = [1,2,3];
    foreach($x as &$ref){
        $ref += 100;
    }

    /* $x === [101, 102, 103]
    at this point, $ref is bound to the last element of $x, that's OK */

    $b = $x;
    /* this should logically copy $x to $b *by value* (COW happens) */

    $b[0] = 0; /* this should force an array copy in memory */

    /* here, $ref should be rebound to the elements of $x by reference */
    foreach($x as &$ref){
        $ref += 100;
    }

    /* at this point, $x === [201, 202, 203] which is correct, $ref refers
    to the last element of $x again, which is OK,
    BUT! As we copied $b by value before, is should stay as is, but the last 
    element of $b changes to 203! */
    var_dump($b);


Expected result:
----------------
array(3) {
  [0]=>
  int(0)
  [1]=>
  int(102)
  [2]=>
  int(103)
}


Actual result:
--------------
array(3) {
  [0]=>
  int(0)
  [1]=>
  int(102)
  [2]=>
  &int(203)
}