cek-login

<?php

session_start();

/* PASSWORD MD5 */
$data = array(
    array(
        'u' => 'admin',
        'p' => '21232f297a57a5a743894a0e4a801fc3'
    )
);

if($_SERVER['REQUEST_METHOD'] == 'POST' && isset($_POST['__login'])){
    $username = isset($_POST['username']) ? $_POST['username'] : null;
    $password = isset($_POST['password']) ? $_POST['password'] : null;

    $login = array(
        'u' => $username,
        'p' => md5($password)
    );

    if(in_array($login, $data)){
        $_SESSION['__valid'] = TRUE;
        header('Location: '.$_SERVER['PHP_SELF']);
    }
    else{
        echo "<script>alert('Wrong!')</script>";
    }

}

?>

<?php if(!isset($_SESSION['__valid'])){ ?>

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Login Page</title>
    <style type="text/css" media="screen">
        .mx-auto{
            margin-left: auto;
            margin-right: auto;
            display: block;
        }
    </style>
</head>
<body>
    <form action="<?= $_SERVER['PHP_SELF'] ?>" method="post" accept-charset="utf-8">
        <input type="text" name="username" class="mx-auto" class="username" placeholder="Username"><br>
        <input type="password" name="password" class="mx-auto" placeholder="Password"><br>
        <button type="submit" name="__login" value="Checking Login" class="mx-auto">Login</button>
    </form>
</body>
</html>

<?php exit();} ?>