How to use session inside webpages?

Question

I am trouble with session; I know it theoretically but I encountered with it how to use session , transferring username to

Answer 1

After the line

$result=mysql_query($sql);

add

if ($data = mysql_fetch_array($result)) {
    $_SESSION['user'] = $data['usermail'];
}

Now session created.Call this session in jcte/index.php page as:

Unset the session in logout.php page as: