Is using FILTER_SANITIZE_STRING sufficient for sanitizing user inputs before inserting them into a database, or should additional measures like htmlentities or htmlspecialchars be taken?

Using FILTER_SANITIZE_STRING alone is not sufficient for sanitizing user inputs before inserting them into a database. It is important to also use functions like htmlentities or htmlspecialchars to prevent potential XSS attacks by escaping special characters. These functions help to ensure that user input is properly sanitized before being stored in the database.

$user_input = $_POST['user_input'];

// Sanitize user input using FILTER_SANITIZE_STRING and escape special characters
$sanitized_input = filter_var($user_input, FILTER_SANITIZE_STRING);
$sanitized_input = htmlspecialchars($sanitized_input);

// Insert sanitized input into the database
// $stmt = $pdo->prepare("INSERT INTO table_name (column_name) VALUES (:input)");
// $stmt->bindParam(':input', $sanitized_input);
// $stmt->execute();