How can beginners protect their PHP code from hackers and malware attacks?

Beginners can protect their PHP code from hackers and malware attacks by implementing security measures such as input validation, using prepared statements for database queries, escaping output data, and keeping their PHP version up to date. They should also avoid storing sensitive information in plain text and regularly scan their code for vulnerabilities. ``` // Example of input validation $username = $_POST['username']; if (!preg_match("/^[a-zA-Z0-9]*$/", $username)) { die("Invalid username format"); } // Example of using prepared statements for database queries $stmt = $pdo->prepare("SELECT * FROM users WHERE username = ?"); $stmt->execute([$username]); $user = $stmt->fetch(); // Example of escaping output data echo htmlspecialchars($user['username'], ENT_QUOTES, 'UTF-8'); ```