query login

<?php
        //memulai session
        session_start();

        //Include file koneksi ke database
        require_once('koneksi.php');

        //fungsi untuk membersihkan nilai yang diterima dari form. mencegah SQL injection
        function clean($str) {
                $str = trim($str);
                if(get_magic_quotes_gpc()) {
                        $str = stripslashes($str);
                }
                return mysql_real_escape_string($str);
        }

        //mengambil nilai inputan form dan menyimpan ke variabel
        $username = clean($_POST['username']);
        $password = clean($_POST['password']);


        //buat query
        $qry="SELECT * FROM login WHERE username='{$username}' AND password='{$password}'";
        $result=mysql_query($qry) or die("ada kesalahan query [{$sql}] dengan pesan:".mysql_error());

        //Check   query  telah sukses
        //if($result) {
                if(mysql_num_rows($result) == 1) {
                        //Login berhasil
                        session_regenerate_id();
                        $user = mysql_fetch_assoc($result);
                        ("username");//isi variabel session dengan query tabel
                        ("password");//isi variabel session dengan query tabel
                        session_write_close();
                        echo "<meta http-equiv='refresh' content='0; url=admin/index.php'>";                    exit();
                }else {
                        //Login gagal akan diarahkan ke halaman failed login
                        echo "<script>alert('Anda Gagal Login Ulangi Kembali');</script>";
                        echo "<meta http-equiv='refresh' content='0; url=index.php'>";
                        exit();
        /*        }
        }else {
                die("Query failed");
        }*/
?>