登录 2shared 站点时，使用 curl-php 不起作用登录到站点

>我正在尝试使用 curl-php 登录 2shared，但由于某种原因，它只返回我的登录页面，并且没有在 cookie 文件中设置正确的 cookie。下面是我的代码。感谢您的任何帮助。

$user = "";
$pass = "";
$cookie = "cookie.txt";
$jsonp = 'jsonp'.time();
if (file_exists($cookie)) {
    unlink($cookie);
}
$post = array(
    "login" => $user,
    "password" => $pass,
    "callback" => $jsonp
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://www.2shared.com/login?callback=".$jsonp);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('X-Requested-With: XMLHttpRequest'));
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);    
curl_setopt($ch, CURLOPT_REFERER, 'http://www.2shared.com/');       
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20100101 Firefox/12.0");
curl_setopt($ch, CURLOPT_ENCODING, "UTF-8" );
$return = curl_exec($ch);
curl_close($ch);
echo $return;

编辑：

当我通过浏览器登录并通过HTTP分析器监视流量时，我注意到点击登录按钮后它会返回此数据并重定向到loginRedirect对象，我注意到它设置了一些cookie，这些cookie在我执行php-curl请求时不会出现：

{
    "ok":true,
    "rejectReason":"",
    "loginRedirect":"http://www.2shared.com/account/homeDoorway.jsp;jsessionid=3F253C7C641C7A8402D4AC9872C1CEAE.dc282?rand=0.8112776952920494",
    "loggedIn":"myemail@email.com",
    "needActivation":false
}

但是当尝试使用上面的代码 curl-php 登录时，它会返回我以下数据：

jsonp1339804887({
    "ok":true,
    "rejectReason":"",
    "loginRedirect":"http://www.2shared.com/login.jsp?sessionUnavailable=1",
    "loggedIn":"",
    "needActivation":false
})