natas/natas21/reverse2.php

<html>
<head><link rel="stylesheet" type="text/css" href="http://natas.labs.overthewire.org/css/level.css"></head>
<body>
<h1>natas21 - CSS style experimenter</h1>
<div id="content">
<p>
<b>Note: this website is colocated with <a href="http://natas21.natas.labs.overthewire.org">http://natas21.natas.labs.overthewire.org</a></b>
</p>
<?php

session_start();

// if update was submitted, store it
if(array_key_exists("submit", $_REQUEST)) {
    foreach($_REQUEST as $key => $val) {
        $_SESSION[$key] = $val;
    }
}

if(array_key_exists("debug", $_GET)) {
    print "[DEBUG] Session contents:<br>";
    print_r($_SESSION);
}

// only allow these keys
$validkeys = array("align" => "center", "fontsize" => "100%", "bgcolor" => "yellow");
$form = "";

$form .= '<form action="index.php" method="POST">';
foreach($validkeys as $key => $defval) {
    $val = $defval;
    if(array_key_exists($key, $_SESSION)) {
        $val = $_SESSION[$key];
    } else {
        $_SESSION[$key] = $val;
    }
    $form .= "$key: <input name='$key' value='$val' /><br>";
}
$form .= '<input type="submit" name="submit" value="Update" />';
$form .= '</form>';

$style = "background-color: ".$_SESSION["bgcolor"]."; text-align: ".$_SESSION["align"]."; font-size: ".$_SESSION["fontsize"].";";
$example = "<div style='$style'>Hello world!</div>";

?>

<p>Example:</p>
<?=$example?>

<p>Change example values here:</p>
<?=$form?>

<div id="viewsource"><a href="index-source.html">View sourcecode</a></div>
</div>
</body>
</html>