Apache crashes when using WHILE loop to traverse SQL query results (Apache Users)

I'm using a simple php program that I found in a PHP/SQL book. The PHP program queries a MySQL table and uses a WHILE loop to traverse the results array of the query and display on screen. However, there seems to be a problem with my environment and using a WHILE loop as every time I run the program I get the error "Apache HTTP server stopped working and was closed".

<?php
/* Program: petDisplay.php
* Desc:    Displays all pets in selected category.
*/
?>
<html>
<head><title>Pet Catalog</title></head>
<body>
<?php

$user="root";
$host="localhost";
$password="PASSWORD";
$database = "am";
$cxn = mysqli_connect($host,$user,$password,$database)
         or die ("couldn't connect to server");
$pettype = "horse"; //horse was typed in a form by user
$query = "SELECT * FROM Pet WHERE petType='$pettype'";
$result = mysqli_query($cxn,$query)
            or die ("Couldn't execute query.");

/*Display results in a table */
$pettype = ucfirst($pettype)."s";

echo "<h1>$pettype</h1>";
echo "<table cellspacing='15'>";
echo "<tr><td colspan='3'><hr /></td></tr>";
while($row = mysqli_fetch_assoc($result))
{
     extract($row);

     $f_price = number_format($price,2);
     echo "<tr>\n
            <td>$petName</td>\n
            <td>$petDescription</td>\n
            <td style='text-align: right'>\$$f_price</td>\n
           </tr>\n";
     echo "<tr><td colspan='3'><hr /></td></tr>\n";
}
echo "</table>\n";
?>
</body></html>