Description:
------------
After your asked me to try an other bug with PHP 5.1.0, i tryed to run my unit tests on it.
All passes, except the following. I don't know if it's a new PHP 5.1.0 feature, but i don't think that this behaviour is really useful and it can be very confusing too.

PHP version : php5-200410111030

Reproduce code:
---------------
<?php

function haricow($a = 'one') {
	var_dump($a);
	$a = 'two';
}

haricow();
haricow();

Expected result:
----------------
string(3) "one"
string(3) "one"

Actual result:
--------------
string(3) "one"
string(3) "two"