on your class page, the form that sets the sessions is:
<form id="form1" name="form1" method="post"  action="standbyconfirm.php">
        <input name="classid" type="hidden" id="classid" value="<?php echo $row_classRS['classid']; ?>" />
        <input name="inid" type="hidden" id="inid" value="<?php echo $row_rsInstance['instanceid']; ?>" />
        <input name="addtostandby" type="submit" id="addtostandby" value="Filled: Request Stand-by" />
    </form>
this is posting to the standbyconfirm.php page.
on the standby confirm page, you have the following code to set the sessions:
<?php
if (!session_id()) session_start();
if($_SESSION["standbyClassID"] < '1')     {
  $_SESSION["standbyClassID"] = "".((isset($_POST["classid"]))?$_POST["classid"]:"")  ."";
}
if (!session_id()) session_start();
if($_SESSION["standbyInstanceID"] < '1')     {
  $_SESSION["standbyInstanceID"] = "".((isset($_POST["inid"]))?$_POST["inid"]:"")  ."";
}
?>
this will only trigger if the sessions are already set to something less than 1. change that to trigger of the form elements instead:
<?php
if (!session_id()) session_start();
if(isset($_POST["classid"]))     {
  $_SESSION["standbyClassID"] = "".((isset($_POST["classid"]))?$_POST["classid"]:"")  ."";
}
if (!session_id()) session_start();
if(isset($_POST["inid"]))     {
  $_SESSION["standbyInstanceID"] = "".((isset($_POST["inid"]))?$_POST["inid"]:"")  ."";
}
?>

