problem with store cart details and summary

i puted de code in /html:
<?php
mysql_free_result($rsSeo);

mysql_free_result($rsNovedades);

mysql_free_result($rsUsuario);
?>
<?php
// Initialize the session.
// If you are using session_name("something"), don't forget it now!
session_start();

// Unset all of the session variables.
$_SESSION = array();

// If it's desired to kill the session, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) {
$params = session_get_cookie_params();
setcookie(session_name(), '', time() - 42000,
$params["path"], $params["domain"],
$params["secure"], $params["httponly"]
);
}

// Finally, destroy the session.
session_destroy();
?>

--- in de two tables the wrotte the same OrderReferenceID, but the order sumari the do well the same the two actions, but with the samen OrderReferenceID. BUT the table orders details, the do the same thing they rewrite the order with the second action.

MAY BE a have te wriete someelse in the code you told me befere..some session?, for the OrderReferenceID i use the ecartd: <?php echo session_id(); ?>, that that writte a long OrderReferenceID, for example:831607a670e5605028633c5cf9eda349

In the order sumary is working fine, still put the same OrderReferenceID, but do not rewrite the information, but in te order detail still rewrite de order detail if the user buy for second time witout close the explorer.

THANKS