Which database connection is best? [duplicate]

I started working and I'm updating the company system, it currently uses this connection:

$link = mysqli_connect("0.0.0.0", "teste", "teste", "teste");
mysqli_set_charset($link, "utf8");

if (mysqli_connect_errno()) {
    printf("<br> Nao foi possivel conectar. Erro: %s\n", mysqli_connect_error());
    exit();
}

$database_host = "0.0.0.0";
$database_user = "teste";
$database_password = "teste";
$database_db = "teste";

$conexao = new mysqli($database_host, $database_user, $database_password, $database_db);
mysqli_set_charset($conexao, "utf8");
if ($conexao->connect_error) {
    die("A conexão falhou!");
}
date_default_timezone_set("America/Sao_Paulo");

I've learned and use this type:

class ConexaoBanco extends PDO {

    private static $instancia = null;

    public function ConexaoBanco($dsn, $usuario, $senha) {
        //Construtor da classe pai PDO
        parent::__construct($dsn, $usuario, $senha);
    }

    public static function getInstancia() {
        if (!isset(self::$instancia)) {
            try {
                // Cria e retorna uma nova conexão
                self::$instancia = new ConexaoBanco("mysql:dbname=teste;host=0.0.0.0", "teste", "teste");
            } catch (Exception $e) {
                echo 'Erro ao conectar o banco de dados!';
                exit();
            }
        }
        return self::$instancia;
    }
}

Which of the two is better? Why?