By default the session variables last since your are in the browser.
The session time deponds on the server configuration but by defult its 24 minutes or 1440 seconds.
The session generated for individuals user are unique i.e. it is the unique identification of user and is known by session id .
When the session starts , either it retrieves its existing session id ( generally from session cookie ) or regenerate new session id .
It is defined as the super global variable $_SESSION .
The session by default stored in the tmp and session.save_path variable influence the path of the session storage location which can be updated by the server administrator.
You must need tho start the session before session assigning the values in session , which can be done as ..
session_start() // Start the session
$_SESSION[‘php’] = ‘Working with the session variable ‘ ; //storing the value in session
print_r($_SESSION); // Print the values stored in session
Array([php] => Working with the session variable );
You can use session_destroy() function to destroy all the session or
session_unset() to unset all the session values .
session_regenerate_id() function to regenerate new session id .
Please leave a comment for any query ..