เกี่ยวกับล็อกอิน สร้างระบบล็อกอินอ่ะค่ะ แล้วมีส่วนของการสมัครสมาชิก เวลาบันทึกลงฐานข้อมูล

<form method="post" name="form2" action="chklogin.php" onSubmit="return chkdata();">
  <table width="200" border="1" cellspacing="0" bordercolor="#FF9FAA">
    <? if($cus_username != "" && $cus_username != NULL){ ?>
    <tr>
      <td colspan="2" bgcolor="#FF9FAA" >
        <span class="style5"><strong>ยินดีต้อนรับคุณ </strong> <span class="style7">:: </span>
        <?
		
		include "connect.php";
		
	  		$sql="select c_name,c_lastname from tb_customer where  c_username='$cus_username'";
			$query=mysql_query($sql);
			$result=mysql_fetch_array($query);
			
				$name_cus=$result["c_name"];
				$lastname_cus=$result["c_lastname"];
				
				echo "<b>$name_cus</b>&nbsp;&nbsp;<b>$lastname_cus</b>";
	  ?> 
        </span></td>
    </tr>
    <tr>
      <td colspan="2" align="left" bgcolor="#ECF9FF"> <span class="style5"><br />
        <img src="file:///C|/AppServ/www/rose/icon/User-Coat-Red-icon.png" width="15" height="15" border="0" align="baseline" /> <a href="myaccount.php"> ข้อมูลส่วนตัว</a><br />
      </span><span class="style5"><br />
        <img src="icon/iCal-empty-icon.png" width="15" height="15" align="absbottom" /> ประวัติการสั่งซื้อ <a href="register_edit.php" class="style5"><br />
        <br />
      </a></span> <span class="style5"><img src="file:///C|/AppServ/www/rose/icon/Button-Close-icon.png" width="15" height="15" align="absbottom" /> <a href="script_logout.php">ออกจากระบบ</a></span></td>
    </tr>
    
    <? }else{ ?>
    <tr bgcolor="#FF9FAA">
      <td colspan="2" align="center" bgcolor="#FFFFFF"><img src="icon/ebus_22.jpg" width="190" height="25" /></td>
    </tr>
    <tr bgcolor="#FF9FAA" class="normal_font" >
      <td width="43%" align="right" ><span class="style5">username :: </span></td>
      <td width="57%" class="normal_font"><input name="username" type="text" id="username" style="width:100px;" /></td>
    </tr>
    <tr bgcolor="#FF9FAA" class="normal_font">
      <td align="right" ><span class="style5">password :: </span></td>
      <td class="normal_font"><input name="password" type="password" id="password" style="width:100px;" maxlength="20" /></td>
    </tr>
    <tr>
      <td height="40" colspan="2" align="center" valign="top" bgcolor="#FFFFFF"><input name="go" type="hidden" id="go" value="<?=$go?>" />
          <input name="id" type="hidden" id="id" value="<?=$id?>" />
          <br />
          <span class="style5">
          <input name="submit" type="submit" value="ยืนยัน" />
          <input name="Reset" type="reset" value="ยกเลิก" />
          <br />
          <br />
        [ <img src="icon/ebus_02.jpg" width="20" height="15" border="0" /> <a href="register.php">สมัครสมาชิก</a> ] [ <img src="icon/ebus_05.jpg" width="20" height="15" /> ลืมรหัสผ่าน ] </span> </td>
    </tr>
    <? } ?>
  </table>
</form>
  <script language="javascript">
function chkdata()
{
    if(document.form2.username.value == ""){
        alert('กรุณากรอกชื่อที่ใช้ในระบบด้วยน่ะครับ');
        document.form2.username.focus();
      	return false;
}  
    if(document.form2.password.value == ""){
        alert('กรุณากรอกรหัสผ่านด้วยน่ะครับ');
        document.form2.password.focus();       
       	return false;
}
document.form2.submit();
}
</script>

<? 

	include"connect.php" ; 
	include "function_chklogin.php";
	
	$username=$_POST["username"];
	$password=$_POST["password"];
	$go=$_POST["go"];
		if(empty($go)){ $go="index.php"; }
	
	$sql="select c_id from tb_customer where c_username='$username' and c_password='$password' ";
	$query=mysql_query($sql) or die("SQL Error $sql");
	$num=mysql_num_rows($query);
	$data=mysql_fetch_array($query);
	
		if($num>0){
			$_SESSION["ss_id"]=$data["c_id"];
			$_SESSION["ss_username"]=$username;
			$_SESSION["ss_password"]="yes";
		
			echo "<script>window.location.href('$go?go=$go')</script>";
		}else{
			echo "<script>alert('user password ไม่ถูกต้องกลับไปตรวจสอบอีกครั้ง');history.back();</script>";
		}
?>

<? 

	include"connect.php" ; 
	include "function_chklogin.php";
	
	$username=$_POST["username"];
	$password=$_POST["password"];
	$go=$_POST["go"];
		if(empty($go)){ $go="index.php"; }
	
	$sql="select c_id from tb_customer where c_username='$username' and c_password='$password' ";
	$query=mysql_query($sql) or die("SQL Error $sql");
	$num=mysql_num_rows($query);
	$data=mysql_fetch_array($query);
	
		if($num>0){
			$_SESSION["ss_id"]=$data["c_id"];
			$_SESSION["ss_username"]=$username;
			$_SESSION["ss_password"]="yes";
		
			echo "<script>window.location.href('$go?go=$go')</script>";
		}else{
			echo "<script>alert('user password ไม่ถูกต้องกลับไปตรวจสอบอีกครั้ง');history.back();</script>";
		}
?>