Мой метод по получению сессии:
function get_session ()
{
$curl = curl_init();
curl_setopt($curl,CURLOPT_URL, $this->site . "/index.php");
curl_setopt($curl,CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT']);
curl_setopt($curl,CURLOPT_TIMEOUT,60);
curl_setopt($curl,CURLOPT_RETURNTRANSFER,1);
$result = curl_exec($curl);
curl_close($curl);
preg_match("/\SID=(.*)\"/Ui",$result,$session);
$this->session = $session[1];
}