问尝试从数据库检索数据时出现mysql_fetch_array()错误

EN

<?php require_once('Connections/MyDatabase.php'); ?>
<?php
session_start();
?>

<?php 
$cartTotal = 0;
if(isset($_POST['CheckoutBTN']))
{
    date_default_timezone_set('Asia/Singapore');
    $time=date('D,F j, Y, H:i:s A');
    $uname = $_SESSION['MM_Username'];
foreach ($_SESSION["supermarketcart"] as $each_item)
    {

     $item_id = $each_item['item_id'];
        $sql = mysql_query("SELECT * FROM supermarket WHERE id = '$item_id' LIMIT 1");
      while($row = mysql_fetch_array($sql)){
    $productdes = $row['description'];
    $price = number_format($row['price'],2);
    $size = $row['packaging'];
    $itemqty = $each_item['quantity'];

  $pricetotal = $price * $each_item['quantity'];
  $cartTotal = number_format($pricetotal + $cartTotal,2);

    $checkout="INSERT INTO supermarketcart (itemid, productdes, package, itemprice, qty, username, ddate) VALUES 
                           ('$item_id', '$productdes', '$size', '$price','$itemqty','$uname','$time')";
    mysql_query($checkout)or die(mysql_error());

       }
    }
}

?>
<?php
//initialize the session
if (!isset($_SESSION)) {
  session_start();
}

// ** 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']);

  $logoutGoTo = "login.php";
  if ($logoutGoTo) {
    header("Location: $logoutGoTo");
    exit;
  }
}
?>
<?php
if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($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;
}
}

$colname_cart = "-1";
if (isset($_SESSION['MM_USERNAME'])) {
  $colname_cart = $_SESSION['MM_USERNAME'];
}
mysql_select_db($database_MyDatabase, $MyDatabase);
$query_cart = sprintf("SELECT * FROM supermarketcart WHERE username = %s", GetSQLValueString($colname_cart, "text"));
$cart = mysql_query($query_cart, $MyDatabase) or die(mysql_error());
$row_cart = mysql_fetch_assoc($cart);
$totalRows_cart = mysql_num_rows($cart);

mysql_select_db($database_MyDatabase, $MyDatabase);
$query_user_info = "SELECT * FROM user_data";
$user_info = mysql_query($query_user_info, $MyDatabase) or die(mysql_error());
$row_user_info = mysql_fetch_assoc($user_info);
$totalRows_user_info = mysql_num_rows($user_info);
?>