how long do $_POST variables stay active, and how does PHP decide what goes in the post array?
<pre>

$user = $_POST['user'];
$pass = $_POST['pass'];

if(isset($user) && $user !== null){
   if(isset($pass) && $pass !== null)
    echo 'true'
   else
    echo 'false';
}


</pre>

<pre>
$.post('script.php',{user: 'username'}) -> posts to the script, but doesn't
return anything, as in this case it would return false

<em>5 minutes later</em>

$.post('script.php',{pass: 'password'}, function(data){
       alert("data returned: " + data);
});

</pre>