What are the best practices for troubleshooting and resolving PHP session-related problems, especially when data is not being retained between pages?

Issue: PHP session-related problems can occur when data is not being retained between pages. This can be caused by various factors such as incorrect session configuration, expired sessions, or session data not being properly stored or retrieved. To troubleshoot and resolve PHP session-related problems, ensure that session_start() is called at the beginning of each page where session data is needed. Additionally, check the session configuration settings in php.ini to make sure they are correctly set. If session data is not being retained, verify that session variables are being properly set and accessed throughout the application.

<?php
// Start the session
session_start();

// Set session variables
$_SESSION['username'] = 'john_doe';
$_SESSION['email'] = 'john.doe@example.com';

// Retrieve session variables
$username = $_SESSION['username'];
$email = $_SESSION['email'];

// Output session data
echo "Username: " . $username . "<br>";
echo "Email: " . $email;
?>