<?php
if(isset($_POST['langselector'])) {
    setcookie("lang", $_POST['langselector'], time() + (86400 * 30), "/"); // 86400 * 30 = 1 dag
    header("Refresh:0");
}
?>
<div class="topbar">
    <div class="container">
        <?php
        $cookie = $_COOKIE['lang'];

        if($cookie == "nl") {
            $img = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAKUAAABuCAMAAABx2iOfAAAAFVBMVEX///+uHCghRousCx3Fenp6hK0TP4gBU4NHAAAAd0lEQVR4nO3OwQnDQBAAsY3juP+S08I9BsyCVIHms8G8HThi2bHsWHYsO5Ydy45lx7Jj2bHsWHYsO5Ydy45lx7KzZPndYO4NBgAAAAAAOPfbYJ4N5trAsmPZsexYdiw7lh3LjmXHsmPZsexYdiw7lh3LjmXHsvMHa35PSF7g9JQAAAAASUVORK5CYII=";
            $lang = "en";
        }
            else {
            $img = "/assets/images/en.png";
            $lang = "nl";
        }
        ?>
        <form action="" method="POST">
            <button type="submit" class="lang" href="#" value="<?php echo $lang; ?>" name="langselector">
                <img style="height: 15px;" src="<?php echo $img; ?>">
            </button>
        </form>
    </div>
</div>