Description:
------------
I assign something by-reference to a variable. If I assign the same stuff again to the same variable by-value, this assignment is ignored.

In the reproduce code, $bar first is a reference to $foo. $bar is modified via array_pop(). This modifies $foo, too.

Then, $foo is assigned to $bar by-value. Again, $bar is modified via array_pop(). And again, $foo is modified too, which should not happen, because $bar should not be a reference to $foo any more.

An

   unset($bar);

right before the second assignment fixes the issue.

Reproduce code:
---------------
$foo = array(1, 2, 3, 4, 5);
$bar =& $foo;
array_pop($bar);
var_dump($foo);
$bar = $foo;
array_pop($bar);
var_dump($foo);

Expected result:
----------------
array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
}
array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
}

Actual result:
--------------
array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
}
array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}