check login

<?php

include "../config/koneksi.php";
function antiinjection($data)
{
    $filter_sql = mysql_real_escape_string(stripslashes(strip_tags(htmlspecialchars($data,ENT_QUOTES))));
    return $filter_sql;
}

$username = antiinjection($_POST['username']);
$pass = antiinjection(md5($_POST['password']));
$sql="SELECT *
    FROM admins
    WHERE
    username='$username'
    AND password='$pass'
    AND blokir='N'";
$login=mysql_query($sql)or die("$sql ".mysql_error());
$ketemu=mysql_num_rows($login);
$r=mysql_fetch_array($login);

// Apabila username dan password ditemukan
if ($ketemu > 0){
session_start();
    session_register("namauser");
    session_register("namalengkap");
    session_register("passuser");
    session_register("leveluser");

    $_SESSION[namauser] = $r[username];
    $_SESSION[namalengkap] = $r[nama_lengkap];
    $_SESSION[passuser] = $r[password];
    $_SESSION[leveluser] = $r[level];

    header('location:menu.php?aksi=home');
}
else
{
    echo "<link href='css/screen.css' rel='stylesheet' type='text/css'><link href='css/reset.css' rel='stylesheet' type='text/css'>";
    echo "<center><br><br><br><br><br><br><b>LOGIN GAGAL! </b><br>
    Username atau Password Anda tidak benar.<br>";
?><input type=button class='tombol' value='ULANGI LAGI' onclick=location.href='index.php'></a></center><?php

}
?>