cURL di PHP melalui proxy ISA server

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, 0);

curl_setopt($ch, CURLOPT_PROXY,'alamat.proxyisa.nya');
curl_setopt($ch, CURLOPT_PROXYPORT,'8080');

curl_setopt( $ch, CURLOPT_PROXYAUTH, CURLAUTH_NTLM ); 

curl_setopt ($ch, CURLOPT_PROXYUSERPWD, 'username:password'); 

$content = curl_exec($ch);
curl_close($ch);