Description:
------------
If this is a not a bug, sorry. But I think the behaviors of script execution and object destruction changed in PHP 5.0.5 without notice.

I created a session handler which uses a database object to query a MySQL DB to load/save sessions. The object is a PEAR::DB instance created with mysqli factory; the session handler is a simple object with methods being passed to session_set_save_handler(). The session object has a reference to the database object to query the database.

A problem started to occur when upgrading from PHP 5.0.4 to PHP 5.0.5 on both Windows (XP SP2) and Linux. On Linux, it is not possible to close a session using my own session handler because the database object is already destroyed (read disconnected - the object was still there but not connected - I suspect the use of OO interface of mysqli in PEAR::DB). On Windows, this issue occurs only when functions die() or exit() are used.

Additionally, with E_ALL, I have the following error message:

Unknown: A session is active. You cannot change the session module's ini settings at this time. in Unknown on line 0

Reproduce code:
---------------
My session handler:
class DB_Session
{
  private $db; // instance of PEAR::DB(mysqli)
  public __construct($db) { $this->db = $db; }
  public open($save_path, $session_name); // to open session
  public close(); // to close session
  public read($id); // to read the session data
  public write($id, $sess_data); // to write session data
  public destroy($id); // to delete the session in DB
  public gc($maxlifetime); // my garbage collector
  public start() // to start the session
  {
    ini_set('session.hash_bits_per_character', 5);
    ini_set('session.hash_function', 1); // SHA1
    session_set_save_handler(
        array($this, "open"),
        array($this, "close"),
        array($this, "read"),
        array($this, "write"),
        array($this, "destroy"),
        array($this, "gc")
    );
    session_start();
  }
}

$db = PEAR::connect('mysqli://user:pass@host/db');
$session = new DB_Session($db);

// on Linux, $session->write() raises an error (PEAR::DB
// object disconnected)
// this error occurs in Windows when die() or exit is called

Expected result:
----------------
In PHP 5.0.4, the database object is still connected when the session handler is called to write the session data. I expected the same behavior in PHP 5.0.5, i.e.:

- database object is created
- session object is created, database object passed to constructor
- session is read (ok)
- script execution ends, session is written (ok)
- session is closed (does nothing, db object might be used elsewhere)

Actual result:
--------------
The script executes correctly, but the session isn't saved because method write() fails to query database to record new session data. I have the following behavior:

- database object is created
- session object is created, database object passed to constructor
- session is read (ok)
- script execution ends, session is written (failed - db object disconnected!)

Note that I encountered this error in Windows ONLY when calling exit() or die(). I encountered this issue in every PHP script execution using the custom session handler on Linux (debian sarge).

I know my database object may be destroyed BEFORE my session object, but it doesn't seem to be the case because I can still access its methods. I think it has something to do with the mysqli object (returned by mysqli_connect()) but I'm not sure (I also noticed PEAR::DB(mysqli) isn't handling the persistent option).