Description:
------------
I think its related with 
http://bugs.php.net/bug.php?id=33772

========
"Write and Close handlers are called after destructing objects since PHP
5.0.5. Thus destructors can use sessions but session handler can't use
objects. In prior versions, they were called in the opposite order. It
is possible to call session_write_close() from the destructor to solve
this chicken and egg problem."
===========

It doesn't work since php 5.2.0.

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


function sess_save()
{
	global $db_conn;
	echo is_object($db_conn) ? "OK" : "FAIL";
}

class my_mysqli extends mysqli {
	public function __destruct(){
		sess_save();
	}
}



$db_conn = new my_mysqli($db_host, $db_user, $db_password);


?>


Expected result:
----------------
In php 5 prior 5.2.0 displays:

"OK"



Actual result:
--------------
In php 5.2.0 displays:

"FAIL"