PHP ไม่เก็บค่า ของ $_SESSION เลยอะครับ ช่วยตรวจสอบโค้ดให้ที

<?
	session_start();
	mysql_connect("localhost","root","1234");
	mysql_select_db("member");
	$strSQL = "SELECT * FROM user WHERE username = '".trim($_POST['username'])."' 
	and pass = '".trim($_POST['pass'])."'";
	$objQuery = mysql_query($strSQL);
	$objResult = mysql_fetch_assoc($objQuery);
	
	if(!$objResult)
	{
			echo "Username and Password Incorrect!";
	}
	else
	{
			$_SESSION["userID"] = $objResult["id"];
			$_SESSION["username"] = $objResult["username"];
			$_SESSION["status"] = $objResult["status"];

			session_write_close();
			
			if ($_SESSION["status"] == "user")
			{
				header("location:user.php");
			}
			else
			{
				header("location:admin.php");
			}
	}
	mysql_close();
?>