What are best practices for handling form submissions in PHP to prevent security vulnerabilities?

To prevent security vulnerabilities when handling form submissions in PHP, it is important to sanitize and validate user input to prevent SQL injection, cross-site scripting (XSS), and other malicious attacks. One common best practice is to use prepared statements when interacting with a database to prevent SQL injection attacks. Additionally, input validation should be performed on the server-side to ensure that only expected and safe data is processed.

// Example of handling form submission securely in PHP

// Sanitize and validate user input
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL);

// Use prepared statements to prevent SQL injection
$stmt = $pdo->prepare("INSERT INTO users (username, email) VALUES (:username, :email)");
$stmt->bindParam(':username', $username);
$stmt->bindParam(':email', $email);
$stmt->execute();