Nie wiem dlaczego nie działa

<? function createPostString($aPostFields) { foreach ($aPostFields as $key => $value) { } } $postFields['username'] = 'admin'; $postFields['password'] = 'aaaaa'; $postFields['login'] = 'login'; $postFields['redirect'] = ""; $ch = curl_init('http://127.0.0.1:8888/forum/login.php'); curl_setopt($ch, CURLOPT_POSTFIELDS, createPostString($postFields)); $c=curl_exec($ch); curl_close($ch); ?>