What security risks are associated with allowing users to input language preferences directly in PHP code?

Allowing users to input language preferences directly in PHP code can lead to security risks such as code injection attacks. To mitigate this risk, it is recommended to sanitize and validate user input before using it in the code.

// Sanitize and validate user input for language preference
$language = isset($_POST['language']) ? filter_var($_POST['language'], FILTER_SANITIZE_STRING) : 'default_language';

// Use the sanitized input in the code
echo "Selected language: " . $language;