Description:
------------
Reduced from oss-fuzz #25840:

<?php           
$a = new stdClass; 
$a->a =& $a;
var_dump($a->a = 0);

zend_assign_to_variable() returns variable_ptr, which might be destroyed by the assignment.

The root cause here is the same as in bug #80100, but the reproducer is more fundamental.

Probably the only way to address this is to add a separate version of zend_assign_to_variable() that accepts a zval to copy the value into, and perform that copy before disposing garbage.