update MYsql Database once results return from payment centre

Thats what i need to do but am a little confused how and where to put it. Basically i have the rest of the code from the return but dont know how to implement the update with the information i have.

<div class="<?= $MessageClass ?>">

          <div class="TransactionResultsItem">

                    <div class="TransactionResultsLabel">Payment Processor Response:</div>

                    <div class="TransactionResultsText">

                              <?= $Message ?>

                    </div>

          </div>

<?php if ($DuplicateTransaction == true) { ?>

          <div style="color:#000;margin-top:10px">

                    A duplicate transaction means that a transaction with these details

                    has already been processed by the payment provider. The details of

                    the original transaction are given below

          </div>

          <div class="TransactionResultsItem" style="margin-top:10px">

                    <div class="TransactionResultsLabel">

                              Previous Transaction Response:

                    </div>

                    <div class="TransactionResultsText">

                              <?= $PreviousTransactionMessage ?>

                    </div>

          </div>

<?php } ?>

<div style="margin-top:10px">

<hr/>

<?php

echo "<strong>Variables Passed Back From The Gateway</strong>";

echo "<hr/>";

echo "Message: " . $Message . "<br/>";

echo "Status Code: " . $StatusCode . "<br/>";

echo "Previous Status Code: ". $PreviousStatusCode . "<br/>";

echo "Previous Message: " . $PreviousMessage . "<br/>";

echo "Cross Referrence: " . $CrossReference . "<br/>";

echo "Card Type: " . $CardType . "<br/>";

echo "Card Class: " . $CardClass . "<br/>";

echo "Card Issuer: " . $CardIssuer . "<br/>";

echo "Card Issuer Country Code: " . $CardIssuerCountryCode . "<br/>";

echo "Amount: " . $Amount . "<br/>";

echo "Currency Code: " . $CurrencyCode . "<br/>";

echo "Order ID: " . $OrderID . "<br/>";

echo "Transaction Type: " . $TransactionType . "<br/>";

echo "Transaction Date Time: " . $TransactionDateTime . "<br/>";

echo "Order Description: " . $OrderDescription . "<br/>";

echo "Customer Name: " . $CustomerName . "<br/>";

echo "Address Line 1: " . $Address1 . "<br/>";

echo "Address Line 2: " . $Address2 . "<br/>";

echo "Address Line 3: " . $Address3 . "<br/>";

echo "Address Line 4: " . $Address4 . "<br/>";

echo "City: " . $City . "<br/>";

echo "State: " . $State . "<br/>";

echo "PostCode: " . $PostCode . "<br/>";

echo "Country Code: " . $CountryCode . "<br/>";

echo "Email Address: " . $EmailAddress . "<br/>";

echo "Phone Number: " . $PhoneNumber . "<br/>";

echo "<hr/>";

?>

</div>

          <div style="margin-top:10px">

                    <a href="index.html">Process Another</a>

          </div>

</div>

<!-- Database update using PHP -->

<?php

/*

$host="";

$user="";

$password="";

$database_connection = mysql_connect($host,$user,$password);

if (!$database_connection)

  {

  die('Could not connect: ' . mysql_error());

  }

if ($StatusCode == "0")

{

// Update database for successful transaction (status, stock etc)

}

else

{

// Update database for Failed transaction

}

*/

?>