Session variable not passing between pages

Hi, I've got a form that calculates checkbox values and puts them in a total field called txtTotal. When the user clicks send, I need to pass the total to a payment page.  The form page has PHP

session_start();
$_SESSION['sessTotal'] = $_POST['txtTotal'];

and the payment page has

session_start(); at the top of the page and <?php echo $_SESSION['sessTotal']; ?> where I want the total to display. The total does not carry over to the payment page and I can't work out why.

Here is all the PHP from the form page as I'm pretty new to PHP and not sure if there's a conflict (should session_start appear more than once?)  Thanks guys

<?php require_once('Connections/df.php'); ?> <?php //initialize the session if (!isset($_SESSION)) { session_start(); $_SESSION['sessTotal'] = $_POST['txtTotal']; } // ** Logout the current user. ** $logoutAction = $_SERVER['PHP_SELF']."?doLogout=true"; if ((isset($_SERVER['QUERY_STRING'])) && ($_SERVER['QUERY_STRING'] != "")){   $logoutAction .="&". htmlentities($_SERVER['QUERY_STRING']); } if ((isset($_GET['doLogout'])) &&($_GET['doLogout']=="true")){   //to fully log out a visitor we need to clear the session varialbles   $_SESSION['MM_Username'] = NULL;   $_SESSION['MM_UserGroup'] = NULL;   $_SESSION['PrevUrl'] = NULL;   unset($_SESSION['MM_Username']);   unset($_SESSION['MM_UserGroup']);   unset($_SESSION['PrevUrl']);        $logoutGoTo = "index.php";   if ($logoutGoTo) {     header("Location: $logoutGoTo");     exit;   } } ?> <?php if (!isset($_SESSION)) {   session_start(); } $MM_authorizedUsers = ""; $MM_donotCheckaccess = "true"; // *** Restrict Access To Page: Grant or deny access to this page function isAuthorized($strUsers, $strGroups, $UserName, $UserGroup) {   // For security, start by assuming the visitor is NOT authorized.   $isValid = False;   // When a visitor has logged into this site, the Session variable MM_Username set equal to their username.   // Therefore, we know that a user is NOT logged in if that Session variable is blank.   if (!empty($UserName)) {     // Besides being logged in, you may restrict access to only certain users based on an ID established when they login.     // Parse the strings into arrays.     $arrUsers = Explode(",", $strUsers);     $arrGroups = Explode(",", $strGroups);     if (in_array($UserName, $arrUsers)) {       $isValid = true;     }     // Or, you may restrict access to only certain users based on their username.     if (in_array($UserGroup, $arrGroups)) {       $isValid = true;     }     if (($strUsers == "") && true) {       $isValid = true;     }   }   return $isValid; } $MM_restrictGoTo = "index.php"; if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",$MM_authorizedUsers, $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) {     $MM_qsChar = "?";   $MM_referrer = $_SERVER['PHP_SELF'];   if (strpos($MM_restrictGoTo, "?")) $MM_qsChar = "&";   if (isset($_SERVER['QUERY_STRING']) && strlen($_SERVER['QUERY_STRING']) > 0)   $MM_referrer .= "?" . $_SERVER['QUERY_STRING'];   $MM_restrictGoTo = $MM_restrictGoTo. $MM_qsChar . "accesscheck=" . urlencode($MM_referrer);   header("Location: ". $MM_restrictGoTo);   exit; } ?> <?php if (!function_exists("GetSQLValueString")) { function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") {   if (PHP_VERSION < 6) {     $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;   }   $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);   switch ($theType) {     case "text":       $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";       break;        case "long":     case "int":       $theValue = ($theValue != "") ? intval($theValue) : "NULL";       break;     case "double":       $theValue = ($theValue != "") ? doubleval($theValue) : "NULL";       break;     case "date":       $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";       break;     case "defined":       $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;       break;   }   return $theValue; } } $colname_userDets = "-1"; if (isset($_SESSION['MM_Username'])) {   $colname_userDets = $_SESSION['MM_Username']; } mysql_select_db($database_df, $df); $query_userDets = sprintf("SELECT usersId, userName, password, name FROM users WHERE userName = %s", GetSQLValueString($colname_userDets, "text")); $userDets = mysql_query($query_userDets, $df) or die(mysql_error()); $row_userDets = mysql_fetch_assoc($userDets); $totalRows_userDets = mysql_num_rows($userDets); ?>