include 'Class/Databases.php';
$db = new Databases();
if (isset($_POST["btn"])) {
    /* 
     * Here inserting row as an array paramiter, you should check out databases 
     * insert function there you can see sql syntax. why i am doing this because it's secure 
     * and more efficient way, it's called prepare statement or you 
     * can call binding parameter so that you can prevent sql injection.and also 
     * getting all the $_POST parameter and assigning to a different variables and passing 
     * variables into insertRow() function to achieve desiger result.
     */
    $username = $_POST["username"];
    $firstname = $_POST["firstname"];
    $lastname = $_POST["lastname"];
    $email = $_POST["email"];
    $db->insertRow($param = ["{$username}", "{$firstname}", "{$lastname}", "{$email}"]);
}
?>
<!--head html file into template/header.php file just include here-->
<?php 
$title = "Insert Information";
include 'template/header.php';
?>
<p>
<tr>
    <th>
        <label for="username">Username:</label>
    </th>
</tr>
<tr>
    <td>