Why is using sessions a more efficient method for passing data between PHP files compared to hidden fields or cookies?

Using sessions is a more efficient method for passing data between PHP files compared to hidden fields or cookies because it stores the data on the server-side rather than the client-side. This eliminates the need to send the data back and forth between the client and server with each request, improving performance and security.

// Start a session
session_start();

// Set data in session variable
$_SESSION['username'] = 'example_user';

// Retrieve data from session variable in another PHP file
session_start();
echo $_SESSION['username'];