<?php
$servername = "localhost";
$dbusername = "root";
$dbpassword = "";
$dnname = "horse racing";

$con = mysqli_connect($servername,$dbusername,$dbpassword,$dnname);

if(!$con)
{
    echo 'Database connection problem.';
    die();
}

$query = mysqli_query($con, "SELECT DISTINCT `class` FROM `horses` WHERE `track` = 'katherine'");
while($row = mysqli_fetch_array($query))
{
   echo $row['class'] . '<br />';
}
?>