Issue: https://github.com/php/php-src/issues/7733
Comment Author: cmb69
Before $a = &$value is evaluated, the local $a and the global
$a reference the same value (null). After that reference assignment, the
local $a and the local $value reference the same value (1).
As such, the local $a looses the reference to the value null. That does
not happen with $c, because you're not assigning by-ref.