ขอแนวคิดทำระบบ login โดยรหัสผ่าน เปลี่ยนไปทุกครั้งหลังจากที่ login ครับ

<?
	session_start();
	mysql_connect("localhost","root","root");
	mysql_select_db("mydatabase");
	$strSQL = "SELECT * FROM member WHERE Username = '".trim($_POST['txtUsername'])."' 
	and Password = '".trim($_POST['txtPassword'])."'";
	$objQuery = mysql_query($strSQL);
	$objResult = mysql_fetch_array($objQuery);
	if(!$objResult)
	{
			echo "Username and Password Incorrect!";
	}
	else
	{
			$_SESSION["UserID"] = $objResult["UserID"];
			$_SESSION["Status"] = $objResult["Status"];

			session_write_close();
			
			if($objResult["Status"] == "ADMIN")
			{
				header("location:admin_page.php");
			}
			else
			{
				header("location:user_page.php");
			}
	}
	mysql_close();
?>

function random_password($len)
{
	srand((double)microtime()*10000000);
	$chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
	$ret_str = "";
	$num = strlen($chars);
	for($i = 0; $i < $len; $i++)
	{
		$ret_str.= $chars[rand()%$num];
		$ret_str.=""; 
	}
	return $ret_str; 
}
// echo random_password(8); 
$passw = random_password(7);