Setting php sessions

[tdrsam]

I'm trying to register new users and store their email address and password to a db, which is working fine, but I'm also trying to set a session, so that the page they land on after they register is a protected page.

I'm using a standard form which runs this when the form is submitted:

<?php
// connect to db manager
$link = mysql_connect("localhost", "root", "");
if (!$link) {die('Database Error: Could not connect: ' . mysql_error());}

// select db
$db_selected = mysql_select_db('foo', $link);
if (!$db_selected) {
    die ('Can\'t use foo : ' . mysql_error());
}

// username and password sent from form
$em = mysql_real_escape_string($_POST['email']);
$pw = mysql_real_escape_string($_POST['password']);

// MySQL Insert Statement
$insert = "INSERT INTO users (`email`, `password`) VALUES ('$em',AES_ENCRYPT('$pw','secretKey'))";

// Perform Query
$execute = mysql_query($insert);

// Check result
// Show Error Message If Not Inserted
if (!$execute) {
    $message  = 'Invalid query: ' . mysql_error() . "\n";
    $message .= 'Whole query: ' . $query;
    die($message);
}
// Set Session + Redirect If New User Inserted
elseif(session_id())
{
     // session has been started
     echo '<script type="text/javascript">';
     echo 'document.location.href = "../u/user.php";';
     echo '</script>';
}
else
{
     // session has NOT been started
     session_start();
     echo '<script type="text/javascript">';
     echo 'document.location.href = "../u/user.php";';
     echo '</script>';
}

mysql_close($link);
?>

And at the top of the document for the page `u/user.php` which is where the user is supposed to be redirected to after they register, there's this:

<?php
session_start();
if (empty($_SESSION[''])){
header("location:../index.php");
}
?>

But this redirects me to the `../index.php` page every time I run a test to insert a new user to the db, which means that the session either must be empty or there's a session variable that's missing.

Where am I going wrong? I've only done this once or twice before and not for a while, and I can't remember how this works. I also can't really find information about it. I'm sure it's out there, I just can't find it. I must be googling the wrong phrases.

[Dormilich]

you never set $_SESSION[''], so it's always empty.