How can PHP developers ensure that form data passed through $_POST is properly sanitized and validated to prevent unexpected errors or security vulnerabilities?

Developers can ensure that form data passed through $_POST is properly sanitized and validated by using functions like filter_var() and htmlspecialchars() to sanitize input data and validate it against expected formats. Additionally, they can use prepared statements in database queries to prevent SQL injection attacks. By implementing these measures, developers can reduce the risk of unexpected errors and security vulnerabilities in their PHP applications.

// Sanitize and validate form data passed through $_POST
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL);

// Prevent SQL injection by using prepared statements
$stmt = $pdo->prepare("INSERT INTO users (username, email) VALUES (?, ?)");
$stmt->execute([$username, $email]);