What security considerations should be taken into account when troubleshooting unexpected behavior in PHP form submissions?

When troubleshooting unexpected behavior in PHP form submissions, it is essential to consider security measures to prevent potential vulnerabilities such as SQL injection or cross-site scripting attacks. One way to enhance security is to sanitize and validate user input before processing it in the application. Additionally, implementing measures like input validation, using prepared statements for database queries, and escaping output can help mitigate security risks.

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

// Prepare and execute a safe SQL query
$stmt = $pdo->prepare("INSERT INTO users (name, email) VALUES (:name, :email)");
$stmt->execute(array(':name' => $name, ':email' => $email));

// Output escaped data to prevent XSS attacks
echo htmlspecialchars($name);