Creating a reference to an array element prevents that
particular element from being listed in a foreach-loop.
Instead, the previous element in the array is processed
twice.  Simple PHP script to reproduce the problem:

---------------
<?php
  $A = array(
    'a' => 'A',
    'b' => 'B',
    'c' => 'C');

  /* This works: */
  foreach ($A as $y => $x) {
    echo "y=$y x=$x\n";
  }

  /* This breaks: */
  $x = &$A['b'];
  foreach ($A as $y => $x) {
    echo "y=$y x=$x\n";
  }
?>
-------------------

This results in the following output:

---------------------
X-Powered-By: PHP/4.0.2
Content-type: text/html

y=a x=A
y=b x=B
y=c x=C
y=a x=A
y=b x=A     <== ERROR!!
y=c x=C
-------------------

Note:  I think this is possibly related to bug id #6417