How can PHP developers ensure data privacy and compliance with regulations like GDPR when collecting and visualizing user data?

// Example PHP code snippet for encrypting user data before storing it in a database

// Encrypt user data before storing it in the database
function encryptData($data, $key) {
    $cipher = "AES-256-CBC";
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($cipher));
    $encrypted = openssl_encrypt($data, $cipher, $key, 0, $iv);
    return base64_encode($iv . $encrypted);
}

// Decrypt user data when retrieving it from the database
function decryptData($data, $key) {
    $cipher = "AES-256-CBC";
    $data = base64_decode($data);
    $iv = substr($data, 0, openssl_cipher_iv_length($cipher));
    $encrypted = substr($data, openssl_cipher_iv_length($cipher));
    return openssl_decrypt($encrypted, $cipher, $key, 0, $iv);
}

// Example usage
$data = "Sensitive user data";
$key = "SecretKey";
$encryptedData = encryptData($data, $key);
$decryptedData = decryptData($encryptedData, $key);

echo "Encrypted data: " . $encryptedData . "\n";
echo "Decrypted data: " . $decryptedData . "\n";