login.php

<?php
session_start();
$_SESSION['sesi']   = NULL;

include "include/koneksi_db.php";

$user   = isset($_POST['user']) ? $_POST['user'] : "";
$pass   = isset($_POST['pass']) ? $_POST['pass'] : "";


$qry    = mysql_query("SELECT * FROM admin WHERE username = '$user' AND password = '$pass'");
$sesi   = mysql_num_rows($qry);

if ($sesi == 1) {
    $data_admin = mysql_fetch_array($qry);

    $_SESSION['sesi'] = $data_admin['username'];

    echo "<script>alert('Anda berhasil Log In. Username : $sesi');</script>";
    echo "<meta http-equiv='refresh' content='0; url=admin/index.php?user=$sesi'>";

} else {
    echo "<meta http-equiv='refresh' content='0; url=index.php'>";
    echo "<script>alert('Anda Gagal Log In');</script>";
}

?>