MySQLi OOP connection example PHP

$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

if (mysqli_connect_errno())
{
   printf("Connect failed: %s\n", mysqli_connect_error());
   exit();
}

$query = "SELECT * FROM users WHERE user_id='$userid'";

if ($result = $mysqli->query($query))
{
   while ($row = $result->fetch_assoc())
   {
       echo $row['name'] ."<br />";
   }
   $result->close();
}

$mysqli->close();