secure AJAX update.php with init.php

I have a page that calls update.php via jQuery whenever a input field is changed. How do I check if a user is logged in? do I have to also load init.php at the top of update.php?

I currently use the following code:

<pre>

<?php
require_once 'users/init.php';
if($user->isLoggedIn()){ 
   //some script
}
else{
 echo 'go away!';
}
?>

</pre>


But I wonder if this is the correct way or if there is a better way.

You're exactly right.

if($user->isLoggedIn()){ }

is the way to go. There are other ways to detect if the user variable is set or something like that, but isLoggedIn is the official and most reliable way to do it.