Classes - Connecting with mysqli

This script works with require_once and produces warnings for line 6 when I try to use $mysqli = new... (which I've commented out). Please help me with this script:

[codebox]<?php

require_once "connect_to_mysql.php";

//$mysqli = new mysqli("localhost","user","pw","db");

$result = mysql_query("SELECT * FROM example")

or die(mysql_error());

echo "<table border='1'>";

echo "<tr> <th>Name</th> <th>Age</th> </tr>";

while($row = mysql_fetch_array( $result )) {

echo "<tr><td>";

echo $row['name'];

echo "</td><td>";

echo $row['age'];

echo "</td></tr>";

}

echo "</table>";

//mysqli_close($mysqli);

?> [/codebox]

Thank-you