ทำล็อกอินของเว็บทุกส่วนไว้ที่เดียวกัน และเกี่ยวกับเรื่อง session ช่วยหน่อยนะค่ะ

<?php
session_start() ;

/* add by kergrit(redthird.com) for compatible global variable off/on php.ini */
$user_login = $_POST['user_login'];
$pwd_login = $_POST['pwd_login'];

if(isset($user_login) and isset($pwd_login)) {
include("config.php") ;

?>

<?php 
  include("config.php") ;
$result = mysql_query("select user,password from member where user='$user_login' and password='$pwd_login'") ;
$num = mysql_num_rows($result) ;
if($num<=0) {
				$result = mysql_query("select user,password from admin_member where user='$user_login' and password='$pwd_login'") ;
				$num = mysql_num_rows($result) ;
				if($num<=0) {
					$result = mysql_query("select user,password from employee_member where user='$user_login' and password='$pwd_login'") ;
					$num = mysql_num_rows($result) ;
					if($num<=0) {
					echo "<br><br><center><font size='3' face='MS Sans Serif'><b>รหัสผ่านไม่ถูกต้องครับ</b></font></center>" ;
					print "<meta http-equiv=refresh content=3;URL=index.php>";
					}
						else {

						$dbarr = mysql_fetch_array($result) ;
						if($user_login!=$dbarr['user'] and $pwd_login!=$dbarr['password']) {
						echo "รหัสผ่านไม่ถูกต้อง" ;
						}else {
						$_SESSION['login_true'] = $user_login;
						echo "<meta http-equiv='refresh' content='0 ;url=/employee/home_emp.php'>" ;
						}
						}
						}
				else {

				$dbarr = mysql_fetch_array($result) ;
				if($user_login!=$dbarr['user'] and $pwd_login!=$dbarr['password']) {
				echo "รหัสผ่านไม่ถูกต้อง" ;
				}else {
				$_SESSION['login_true'] = $user_login;
				echo "<meta http-equiv='refresh' content='0 ;url=/admin/home_admin.php'>" ;
				}
				}
				}
else {

$dbarr = mysql_fetch_array($result) ;
if($user_login!=$dbarr['user'] and $pwd_login!=$dbarr['password']) {
echo "รหัสผ่านไม่ถูกต้อง" ;
}else {
$_SESSION['login_true'] = $user_login;
echo "<meta http-equiv='refresh' content='0 ;url=/member/member_detail.php'>" ;
}
}
}
?>