[WeChall] What is your Name?

Mawekl is challenging you. The code might look safe, but it´s a trap!
Again you can see the sourcecode, also as highlighted version.
The ob_start makes it only harder. Oh and visit Security Traps.
Happy Challenging!

GeSHi`ed PHP code for who.php

<?php
chdir('../../../');
define('GWF_PAGE_TITLE', 'What is your Name?');
define('NO_HEADER_PLEASE', '1');
require_once('challenge/html_head.php');$SOLUTION_FLAG = require_once 'challenge/Mawekl/what_is_your_name/solution.php';
GWF_Debug::disableErrorHandler();
error_reporting(E_ERROR);
#########################
# Challenge starts here ##########################
function honeypot($buff)
{
        return str_replace('mawekl', 'Mawekl', $buff);
}ob_start('honeypot',4096);
session_start();
?>
<html><head><title>What is your name?</title><meta name="description" content="What is your name challenge from Mawekl on WeChall. It requires knowledge of PHP, Programming and Exploitation." /><meta name="keywords" content="Hackit,Challenge,PHP,Exploit" /><meta name="author" content="Mawekl" /><meta http-equiv="content-type" content="text/html;charset=UTF-8" /><body><p>
<?phpif(isset($_SESSION['whoami']))
{
        if($_SESSION['whoami'] === 'Mawekl')
                echo 'Welcome Mawekl! Password is '.$SOLUTION_FLAG;
        else                echo 'STRANGER! GO AWAY!';
        unset($_SESSION['whoami']);
}
elseif(isset($_GET['who']))
{        $honeypot = ($_GET['honeypot'] * 1337) + 1.7;
        if(!preg_match('/[^0-9.E+]/',(string)$honeypot) && is_float((int)round($honeypot) - 33))
        {
                $_SESSION['whoami'] = 'Mawekl';
        }        $who = (string)$_GET['who'];
        if($who == 'Mawekl')
        {
                echo 'You are not Mawekl! :[';
                $_SESSION['whoami'] = 'STRANGER';        }
        else
        {
                echo htmlspecialchars('Welcome '.$who.'! ');
                $_SESSION['whoami'] = $who;        }
}
else
{
        echo 'Who are you?!';}
?>
</p></body></html>