Session data deleted on session_start () after page redirection

After a lot of debugging, it seems the problem was (embarrassing) in the session code of my database, and not the typical session problem. You can see my answer related to it here - Thank you

I understand that this may be a duplicate of such questions (for example, one , two , three ), but despite the fact that it seems the best in this, I still have problems.

When using session_set_save_handler () to use my database session class, the session data is cleared when the session starts with session2.php after being redirected from session1.php.

Overview of my observations:

• Data is stored in the database correctly in session1.php
• Data is lost in session_start () in session2.php
• The data is still in the database after the redirect and before calling session_start () in session2.php
• The session identifier remains unchanged and is stored in a cookie, which is correctly sent to the server in the request headers.
• Using default processing in PHP works fine by default

And note:

• exit () used after header ()
• session_start () on each page before exiting

Did I make a silly typo? An error has occurred? Or is it a weird quirk?

Thanks in advance for the help provided.

Here's the code (extracted into the test files to fix this problem):

session1.php

<?php

require_once('session.php');

session_start();  

$_SESSION['KEY'] = 'VALUE PHPSESSID: ' . session_id();

session_write_close();   
header('Location: session2.php');
exit;

session2.php

<?php

require_once('session.php');

session_start();

// Nothing?
var_dump( $_SESSION );

session.php

<?php

define( "DB_HOST", 'localhost' );
define( "DB_USER", '******' );
define( "DB_PWD", '******' );
define( "DB_NAME", '******' );

require_once('class/DatabaseSessionHandler.php');

// Use the DatabaseSessionHandler class to handle sessions
$session_handler = new DatabaseSessionHandler;
// Set up the handler above as the default session handler
session_set_save_handler(
    array($session_handler, 'open'),
    array($session_handler, 'close'),
    array($session_handler, 'read'),
    array($session_handler, 'write'),
    array($session_handler, 'destroy'),
    array($session_handler, 'gc')
);

DatabaseSessionHandler.php

<?php

class DatabaseSessionHandler
{

    protected $connection;
    protected $session_life_time;

    public function __construct()
    {
        // Ensure that everything is closed correctly as 
        // per warning on http://uk3.php.net/session_set_save_handler
        register_shutdown_function( 'session_write_close' );
    }

    public function open( $save_path, $session_name )
    {
        $this->connection = new mysqli( DB_HOST, DB_USER, DB_PWD, DB_NAME );
        $this->session_life_time = get_cfg_var( "session.gc_maxlifetime" );

        if ( $this->connection->connect_error )
            return false;

        return true;
    }

    public function close()
    {
        $this->connection->close();
        return true;
    }

    public function read( $session_id )
    {
        $data = '';

        $statement = $this->connection->prepare( "SELECT `session_data` 
                                                  FROM `session` 
                                                  WHERE `session_id` = ? " );
        $statement->bind_param( "s", $session_id );
        $statement->execute();
        $statement->bind_result( $data );

        return (string) $data;
    }

    public function write( $session_id, $session_data )
    {
        $expiry_time = time() + $this->session_life_time;
        $statement = $this->connection->prepare( "REPLACE INTO `session` 
                                                (`session_id`, `session_data`, 
                                                `expiry_time`)
                                                 VALUES (?, ?, ?)" );
        $statement->bind_param( "ssi", $session_id, $session_data, $expiry_time );

        if ( !$statement->execute() )
            return false;

        return true;
    }

    public function destroy( $session_id )
    {
        $statement = $this->connection->prepare( "DELETE FROM `session` 
                                                    WHERE `session_id` = ?" );
        $statement->bind_param( "s", $session_id );

        if ( !$statement->execute() )
            return false;

        return true;
    }

    public function gc( $max_lifetime )
    {
        $current_time = time();
        $statement = $this->connection->prepare( "DELETE FROM `session` 
                                                    WHERE `expiry_time` < ?" );
        $statement->bind_param( "i", $current_time );

        if ( !$statement->execute() )
            return false;

        return true;
    }

}