оооо,да тут ошибок сразу миллион((

Notice: Undefined variable: PostData in X:\home\localhost\www\chat\room.php on line 27
[Денвер: показать возможную причину ошибки]
Warning: Cannot modify header information - headers already sent by (output started at X:\home\localhost\www\chat\room.php:27) in X:\home\localhost\www\chat\tes.php on line 2

Notice: Undefined variable: otvet in X:\home\localhost\www\chat\room.php on line 48

Warning: Cannot modify header information - headers already sent by (output started at X:\home\localhost\www\chat\room.php:27) in X:\home\localhost\www\chat\room.php on line 48

Notice: Use of undefined constant on - assumed 'on' in X:\home\localhost\www\chat\room.php on line 50
Ответ: венгр!!!

Notice: Use of undefined constant венгр - assumed 'венгр' in X:\home\localhost\www\chat\temp.txt on line 3

Warning: preg_replace() [function.preg-replace]: Unknown modifier '<' in X:\home\localhost\www\chat\room.php on line 107