PHP7 - COUNT ROW DB

// connessione al db
$mysqli = new mysqli("127.0.0.1:3306", "root", "", "polo");

/* check connection */
if ($mysqli->connect_errno) {
    echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;
}


$sql = $mysqli->query("SELECT COUNT(*) FROM orden");
$row = $sql->fetch_row();
$count = $row[0];