รบกวนช่วยดูให้หน่อยครับ มันข้าม loopไป.......

<?PHP
/// รับค่าusername และ password
$username = $_POST['username'];
$password = $_POST['password'];

/// ตรวจสอบ admin login
$sql = "select * from members where a_username = '$username' and a_password = '$password'";
$result = mysql_query($sql) or die ("error = $sql");
$num = mysql_num_rows($result);
$sql2 = "select * from members ";
$objQuery = mysql_query($sql) or die ("Error Query [".$sql."]");
while($objResult2 = mysql_fetch_array($objQuery))
{
	$a_name = $objResult2['a_name'];
	$a_lastname = $objResult2['a_lastname'];
}


/// เช็คเงื่อนไข
if($num > 0 )
{
	$_SESSION['a_user'] = $username;
	date_default_timezone_set('Asia/Bangkok');
	$time = @date("d/m/Y H:i:s");
	file_put_contents('./assets/log/log_file.txt',$username."|$password| <b>LOGIN</b> |IP = [".$_SERVER['REMOTE_ADDR']."]|".$time.PHP_EOL, FILE_APPEND);
	exit("<script>alert('ยินดีต้อนรับเข้าสู่ระบบ คุณ $a_name $a_lastname');window.location='system_index_durable.php';</script>");		
}

else
{

/// ตรวจสอบ memmbers
	$sql2 = "select * from members_2 where m_username = '$username' and m_password = '$password' ";
	$objQuery2 = mysql_query($sql2) or die ("Error Query [".$sql2."]");
	while($objResult = mysql_fetch_array($objQuery2))

       if($num > 0 )
       {
		$m_name = $objResult['m_name'];
		$m_lastname = $objResult['m_lastname'];

		 $_SESSION['b_user'] = $username;
		 date_default_timezone_set('Asia/Bangkok');
	         $time = @date("d/m/Y H:i:s");
	         file_put_contents('./assets/log/log_file.txt',$username."|$password| <b>LOGIN</b> |IP = [".$_SERVER['REMOTE_ADDR']."]|".$time.PHP_EOL, FILE_APPEND);
		exit("<script>alert('ยินดีต้อนรับเข้าสู่ระบบ คุณ $m_name $m_lastname');window.location='system_index_building.php';</script>");
	}
        else
       {
                /// ตรวจสอบ memmbers
	        $sql3 = "select * from members_3 where m_username = '$username' and m_password = '$password' ";
	        $objQuery3 = mysql_query($sql3) or die ("Error Query [".$sql3."]");
	        while($objResult = mysql_fetch_array($objQuery3))

                if($num > 0 )
	        {
		       $m_name = $objResult['m_name'];
		       $m_lastname = $objResult['m_lastname'];

		       $_SESSION['c_user'] = $username;
		       date_default_timezone_set('Asia/Bangkok');
	               $time = @date("d/m/Y H:i:s");
	               file_put_contents('./assets/log/log_file.txt',$username."|$password| <b>LOGIN</b> |IP = [".$_SERVER['REMOTE_ADDR']."]|".$time.PHP_EOL, FILE_APPEND);
		       exit("<script>alert('ยินดีต้อนรับเข้าสู่ระบบ คุณ $m_name $m_lastname');window.location='index.php';</script>");
	       }
               else
               {
                      $_SESSION['c_user'] = $username;
		      $_SESSION['c_pass'] = $password;
		      session_destroy() ;
		      date_default_timezone_set('Asia/Bangkok');
	              $time = @date("d/m/Y H:i:s");
	              file_put_contents('./assets/log/log_file.txt',$username."|$password| <b>LOGIN FAIL</b> |IP = [".$_SERVER['REMOTE_ADDR']."]|".$time.PHP_EOL, FILE_APPEND);
		      exit("<script>alert('ชื่อผู้ใช้ของคุณไม่ได้อยู่ในระบบ กรูณาล๊อกอินเข้าสู่ระบบใหม่');window.location='form_login.php';</script>");
               }
       }
}