The Right Strategy for PHP Session User in Ajax Application - php

Question

I'm writing a Ajax/PHP web application. Most ajax calls are using accessing the user object which is stored in the session.
<?php
session_start();
function session_user()
{
static $session_user = null;
if (!isset($session_user))
{
if (isset($_SESSION['user']))
$session_user = unserialize($_SESSION['user']);
else
$session_user = new User();
}
return $session_user;
}
class User {
public $books_borrowed = array();
public function __construct()
{
}
function __destruct()
{
// store the user object in the session upon destruction
session_start();
$_SESSION[ 'user' ] = serialize( $this );
}
function authorise($user_id, $password)
{
// if the user_id and password match, load books_borrowed from the DB
...
}
function deauthorise()
{
session_destroy();
}
}
?>
Ajax calls access the user object like this:
return session_user()->books_borrowed;
Note that the user object stores itself upon destruction, which, as far as I can tell, happens just before the ajax call return.
The reason I'm storing the user object to the session every time the object is destroyed is that it contains other objects (books) that might change during ajax calls, and neither do I want the book object to 'know' about the user object (for reusability) nor do I want to bother with having to remember storing the user object whenever any information within it changes.
Can someone see anything wrong with this strategy?
Thanks

Answer 1

The main strategy when you make a design for brand new application with ajax is not to think of ajax like about something special. It is regular request performed by browser. Absolutely the same like when you open new page by typing url manually and pressing enter.