Cara Membuat Login PHP

<?php
ob_start();
session_start();
$user        = $_POST['user'];
$password    = $_POST['password'];
$_SESSION['user'] = $user;
$Open = mysql_connect("localhost","root","");
if (!$Open){
die ("Koneksi ke Engine MySQL Gagal !<br>");
                }
$Koneksi = mysql_select_db("login");
if (!$Koneksi){
die ("Koneksi ke Database Gagal !");
}
$sql = "SELECT * FROM admin where user='$user'";
$qry = mysql_query($sql);
$num = mysql_num_rows($qry);
$row = mysql_fetch_array($qry);

if ($num==0 OR $password!=$row['password']) {
?>
<script language="JavaScript">
    alert('Username atau Password tidak sesuai !');
    document.location='index.php';
    </script>
    <?php
}
else {
    $_SESSION['login']=1;
    header("Location: home.php");
    }
    mysql_close($Open); //Tutup koneksi engine MySQL
?>