session_start(); session_regenerate_id();
session_start(); $_SESSION['username'] = 'john_doe'; $_SESSION['last_activity'] = time(); session_regenerate_id(true);
session_start(); if (!isset($_SESSION['initiated'])) { session_regenerate_id(); $_SESSION['initiated'] = true; }In this example, `session_regenerate_id()` is called only once when the session is initiated to prevent session fixation attacks. The package library used in this code is the built-in PHP session extension which can be used without installing any additional packages.