What are the best practices for managing user data in PHP applications, considering the stateless nature of PHP and the need for persistent data storage?

Managing user data in PHP applications can be challenging due to the stateless nature of PHP and the need for persistent data storage. One common approach is to use sessions to store user data across multiple requests. By utilizing sessions, you can maintain user data throughout the user's session on the website.

// Start the session
session_start();

// Store user data in the session
$_SESSION['user_id'] = 123;
$_SESSION['username'] = 'john_doe';

// Retrieve user data from the session
$user_id = $_SESSION['user_id'];
$username = $_SESSION['username'];

// Destroy the session when the user logs out
session_destroy();