Logging out a session properly in PHP

1. The code, explained

Logging out a user in PHP, the right way.

The code, explained

<?php
    // Recover the user's session from the server
    session_start();

    // Free all session variables:
    // Do NOT unset the whole $_SESSION with unset($_SESSION) as this will disable the registering
    // of session variables through the $_SESSION superglobal. (http://php.net/manual/en/function.session-unset.php)
    session_unset();

    // Destroy all 
    session_destroy();
    session_write_close();
    setcookie(session_name(),'',0,'/');
    session_regenerate_id(true);
?>