How can proper debugging techniques be applied to troubleshoot issues related to session management and data retrieval in PHP applications?

Issue: When troubleshooting session management and data retrieval issues in PHP applications, it is important to first check if sessions are being started correctly and if the data is being stored and retrieved properly. This can be done by using debugging techniques such as printing out session variables, checking session configuration settings, and ensuring that data is being properly sanitized before storing or retrieving it.

// Start the session
session_start();

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

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

// Debugging - print out session variables
var_dump($_SESSION);

// Ensure data is properly sanitized before storing or retrieving
$username = filter_var($username, FILTER_SANITIZE_STRING);