What are the best practices for generating and storing unique IDs for user registration in a PHP application?

When generating unique IDs for user registration in a PHP application, it is important to ensure that the IDs are truly unique to avoid conflicts. One common approach is to use a combination of a timestamp and a random string to create a unique identifier. This unique ID can then be stored securely in a database to associate with the user's registration information.

// Generate a unique ID for user registration
$unique_id = uniqid() . bin2hex(random_bytes(4));

// Store the unique ID in the database along with user registration information
$stmt = $pdo->prepare("INSERT INTO users (unique_id, username, email) VALUES (:unique_id, :username, :email)");
$stmt->bindParam(':unique_id', $unique_id);
$stmt->bindParam(':username', $username);
$stmt->bindParam(':email', $email);
$stmt->execute();