--TEST--
Bug #39036 (Unsetting key of foreach() yields segmentation fault)
--FILE--
<?php

$key = 'asdf';

foreach (get_defined_vars() as $key => $value) {
    unset($$key);
}

var_dump($key);

echo "Done\n";
?>
--EXPECTF--
Warning: Undefined variable $key in %s on line %d
NULL
Done