<form action="" method="post">
<input id="login" name="login" placeholder="Gebruikersnaam" value="<?php
if (isset($_POST['login'])) print htmlspecialchars($_REQUEST['login']);
<form action="" method="post">
<input id="login" name="login" placeholder="Gebruikersnaam" value="<?php
if (isset($_POST['login'])) print htmlspecialchars($_REQUEST['login']);