求大神给指点下这些代码有什么有关问题啊为什么session变量不生效
求大神给指点下这些代码有什么问题啊，为什么session变量不生效啊
<?php require_once('Connections/yi*wu.php'); ?>
<?php
if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "")
{
$theValue = get_magic_quotes_gpc() ? stripslashes($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 $theValue;
}
}
mysql_select_db($database_yi*wu, $yi*wu);
$query_Recordset1 = "SELECT * FROM `user`";
$Recordset1 = mysql_query($query_Recordset1, $yi*wu) or die(mysql_error());
$row_Recordset1 = mysql_fetch_assoc($Recordset1);
$totalRows_Recordset1 = mysql_num_rows($Recordset1);
?>
<?php
// *** Validate request to login to this site.
if (!isset($_SESSION)) {
session_start();
}
// ***session变量开始了
$loginFormAction = $_SERVER['PHP_SELF'];
if (isset($_GET['accesscheck'])) {
$_SESSION['PrevUrl'] = $_GET['accesscheck'];
}
if (isset($_POST['Username'])) {
$loginUsername=$_POST['Username'];
$password=(md5($_POST['Password']));
$MM_fldUserAuthorization = "enable";
$MM_redirectLoginSuccess = "index.php";
$MM_redirectLoginFailed = "zhuce.php";
$MM_redirecttoReferrer = false;
//*** 输入账号和密码，判断转向页面。
mysql_select_db($database_yi*wu, $yi*wu);
$LoginRS__query=sprintf("SELECT u_id u_name, pass, enable FROM `user` WHERE u_name=%s AND pass=%s",
//*** 启用符号是这个“·”
GetSQLValueString($loginUsername, "text"), GetSQLValueString($password, "text"));
$LoginRS = mysql_query($LoginRS__query, $yi*wu) or die(mysql_error());
$row_LoginRS = mysql_fetch_assoc($LoginRS);
$loginFoundUser = mysql_num_rows($LoginRS);
if ($loginFoundUser) {
$loginStrGroup = mysql_result($LoginRS,0,'enable');
//*** 声明三个会话变量并分配值
$_SESSION['MM_Username'] = $loginUsername;
$_SESSION['MM_UserGroup'] = $loginStrGroup;
$_SESSION['u_id']= $row_LoginRS('u_id');
if (isset($_SESSION['PrevUrl']) && false) {
$MM_redirectLoginSuccess = $_SESSION['PrevUrl'];
}
header("Location: " . $MM_redirectLoginSuccess );
}
else {
header("Location: ". $MM_redirectLoginFailed );
}
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
</head>
<body>
<h3 align="center">登录系统</h3>
<hr />
<form ACTION="<?php echo $loginFormAction; ?>" id="form1" name="form1" method="POST">
<table width="250" border="1" align="center" cellpadding="0" cellspacing="0">
<tr>
<td colspan="2" nowrap="nowrap" bgcolor="#3366CC"><div align="center"><font color="#FFFFFF">用户登陆</font></div></td>