What are some common pitfalls in handling form submissions in PHP, especially when it comes to preserving user input data?

One common pitfall in handling form submissions in PHP is not properly preserving user input data when the form submission fails validation. To solve this issue, you can store the user input data in session variables and populate the form fields with this data if the submission fails. 

// Start session
session_start();

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate form data
    // If validation fails
    if (/* validation fails */) {
        // Store user input data in session variables
        $_SESSION['name'] = $_POST['name'];
        $_SESSION['email'] = $_POST['email'];
        // Redirect back to the form
        header("Location: form.php");
        exit();
    }
}

// Populate form fields with user input data
$name = isset($_SESSION['name']) ? $_SESSION['name'] : '';
$email = isset($_SESSION['email']) ? $_SESSION['email'] : '';

// Clear session variables
unset($_SESSION['name']);
unset($_SESSION['email']);

Keywords

validation sanitization XSS attacks form resubmission session storage

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