What are common pitfalls when passing data between multiple steps in a PHP form?

Common pitfalls when passing data between multiple steps in a PHP form include using insecure methods like GET requests, not properly validating and sanitizing user input, and losing data when navigating back and forth between form steps. To solve this, you can use sessions to store and retrieve form data securely across multiple steps.

// Start a session
session_start();

// Store form data in session variables
$_SESSION['step1_data'] = $_POST['step1_data'];

// Retrieve form data from session variables in subsequent steps
$step1_data = isset($_SESSION['step1_data']) ? $_SESSION['step1_data'] : '';

// Clear session data when form submission is complete
unset($_SESSION['step1_data']);