Is a connection from my SSL-secured server to an RDS instance automatically encrypted when using mysqli_connect?

I'm trying to determine if I need to use mysqli_ssl_set to encrypt my db layer. I have a standard Amazon RDS instance that I'm connecting to with MySQL user and pass, but I'm unsure if that connection is automatically encrypted. My server is SSL-ready, but does that mean mysqli_connect is encrypted by default? This is my code right now: $connection = mysqli_connect(self::$host, self::$user, self::$password); self::$lastConnection = $connection; $db = "db_prod"; mysqli_select_db($connection, $db); mysqli_set_charset($connection, "utf8mb4"); Do I need to add in mysqli_ssl_set too?