$_session没值

=========================后台判断权限 index.php-嵌入->后台的判断权限文件login.php
if($_session['quan']==1){ //检查$_session['quan']是否不为空!!!
print_r($_session);
echo "登陆成功!";
echo $_session['quan'];
}
if($_session['quan']!=1){ //强制退出后台,跳转到前台
$_session['quan']='0';
echo "---";
echo $_session['quan'];
echo '<script>document.location.href="../login.php";</script>';
// echo PHPF;
// print $_session['quan'];
exit;
}
if($_GET['exit']==1){ //退出删除$_session['quan']='1'
$_session['quan']='0';
echo "退出成功";
echo '<script>document.location.href="../index.php";</script>';
// echo PHPF.'index.php';
exit;
}
=================================前台登陆login.php
include_once('head.php');
// $smarty->assign('title',$title);
echo $blogsystem[0][4].'<br>';
echo $blogsystem[0][6].'<br>';
if(!empty($_POST['firstname']) && !empty($_POST['pwd'])){
// $a=($blogsystem[0][6]=$_POST['firstname']); //用户名
// $b=($blogsystem[0][4]=md5($_POST['pwd'])); //密码

if($blogsystem[0][6]==$_POST['firstname'] && $blogsystem[0][4]==md5($_POST['pwd'])){
$_session['quan']='1';
print_r($_session);
echo $_session['quan'];
echo '<script>alert("kankan");document.location.href="./admin/index.php";</script>';
exit;
}else{
$_session['quan']='0';
echo '<script>alert("nonono");document.location.href="./index.php"</script>';
}

}
print_r($_session);
$smarty->display('login.html');