What security risks are associated with not properly handling user input in PHP forms?

Not properly handling user input in PHP forms can lead to security risks such as SQL injection, cross-site scripting (XSS), and data manipulation attacks. To mitigate these risks, it is important to sanitize and validate user input before processing it in the application. 

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

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

Keywords

SQL injection cross-site scripting (XSS) data validation htmlspecialchars prepared statements

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