login curl

Estou usando o código abaixo para fazer um login mas não passa do formulário de login.

$urlPost ='sistemasweb.sefaz.ba.gov.br/sistemas/DTE/Contribuinte/SSL/ASLibrary/Login';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $urlPost);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, 'ctl00$PHCentro$userLogin=$login&ctl00$PHCentro$userPass=$senha');
curl_setopt ($ch, CURLOPT_COOKIEJAR, 'cookie.txt');
curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20100101 Firefox/21.0');
 curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
 curl_setopt($ch, CURLOPT_TIMEOUT, 30);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
 curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
 curl_setopt($ch, CURLOPT_ENCODING, ''); #Json
 curl_setopt($ch, CURLOPT_HEADER, 1);
 curl_setopt($ch, CURLOPT_VERBOSE, 1);

 $data = curl_exec($ch);