Description:
------------
You can create variables with numeric only names with double dollars. It can be assigned data with double dollar also. 

It will not throw any errors or warnings.

Reproduce code:
---------------
---
From manual page: language.variables.variable
---

<?php

$foo = 123;
$bar = 456;
$$foo = $bar;

echo '<pre>';
print_r(get_defined_vars());

?>

Expected result:
----------------
PHP Fatal Error

Actual result:
--------------
[foo] => 123
[bar] => 456
[123] => 456