AJAX and CI Session (v1.7) w/DB

[eluser]mcjimbob[/eluser]
Hi, I'm having the same problem. I'm starting to add bits of AJAX functionality into a couple of websites.

We have a 'Change Details' page and I have developed a little 'username checker' in mootools. It basically does an AJAX request, checking if the username already exists in the system. Should be simple enough I thought.

The problem was that the AJAX requests seemed to log the user out. I'm now assuming I have the same problem with the session id changing on the AJAX request and the parent page is then out of date.

My initial fix was to add this to the constants.php config file

Code:

define('IS_AJAX', isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest');

Then this in the config.php file

Code:

if(IS_AJAX){
    $config['sess_time_to_update']     = 72000;
}else{
    $config['sess_time_to_update']     = 300;
}

I initially thought it was working but it seems to be a false hope! I've tested it with debug code and the config is being set ($config['sess_time_to_update'] = 72000, expiration is 7200) but that doesn't fix it.

Is this a different problem (tearing my hair out over this one!)