Sessions are global variable that can store values and will be accessible throughout the site .The applications that uses session are user login,cart etc . Session values are stored in the server and it will will have reference to a an session id which will be generated when some one call session_start() and will be stored in the local machine
Once the session id created , this id will be passed to the server along with request and with the help of this the code can fect the values stored in the server .
Session values can be managed with the help of $_SESSION .
Session can be destroyed using the function session_destroy()
Session values will get destroyed if the browser is closed .
echo $_SESSION[‘lan’] ;