How can PHP sessions be effectively utilized to associate user input with specific users in a web application?

To associate user input with specific users in a web application, PHP sessions can be effectively utilized. When a user logs in, a unique session ID can be generated and stored in a session variable. This session ID can then be used to track the user throughout their session, allowing their input to be associated with their specific user account.

// Start the session
session_start();

// Set the session variable with user ID when user logs in
$_SESSION['user_id'] = $user_id;

// Retrieve user ID from session variable when needed
$user_id = $_SESSION['user_id'];