รบกวนช่วยทีค่ะ งมมา 2 วัน เกี่ยวกับ login เข้าสู่ระบบสมาชิกค่ะ

<form method=post action=signin.php>
User : <input type=text name=usermem size=20><br>
Pass : <input type=password name=passmem size=20><br>
<input type=submit value=เข้าระบบ>
</form>

<?php
session_start();
require_once "connectdb.php";

		$sql = "select * from member where usermem = '$_POST[usermem]' and passmem = '$_POST[passmem]'";
		$dbquery = mysql_db_query($db, $sql); 
		$num_rows = mysql_num_rows($dbquery);
		$rowLogin = mysql_fetch_array($dbquery);
		if($num_rows == 1){ 
			$_SESSION['usermem'] = $rowLogin['usermem'];
			echo "<meta http-equiv='refresh' content='0;URL=index.php'>";
		}else{ 
			echo "<meta http-equiv='Content-Type' content='text/html; charset=tis-620' />";
			echo "<script language='javascript'>alert('Invalid Username or Password .. Please Checked');</script>";
			echo "<meta http-equiv='refresh' content='0;URL=login.php'>";
		}

?>

@session_start();
ob_start();
require_once "connectdb.php";
require_once "tdate.php";
if(empty($usermem)) 
{
$showmember = "
<font size=2 color=#cccccc>สวัสดี,บุคคลทั่วไป | <a href=login.php><font color=#ff0000>เข้าสู่ระบบ</font></a> | <a href=member.php><font color=#ffffff>สมัครสมาชิก</font></a></font>
";

}else{
$sql="select * from member where usermem='$usermem'";
						  $db_query=mysql_db_query($db,$sql);
						  $result=mysql_fetch_array($db_query);
						  $idmember=$result[id];
						  $membername=$result[name];
						  $usermember=$result[usermem];
						  $passmember=$result[passmem];
$showmember = "
<font size=2 color=#cccccc>สวัสดี,<font color=#ffffff><u>$membername</u></font>";
}