mysql.php

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // output data of each row
    while($row = mysqli_fetch_assoc($result)) {
    	echo '<pre>';
        print_r($row);
        echo '</pre>';
    }
} else {
    echo "0 results";
}