使用 curl 登录 Joomla 2.5

I'm trying remotely access joomla 2.5 with curl in php. Later I want to create new content too, but for now i have troubles with login. For me is curl new so I don't know what am I doing wrong. I get this message: "Your session has expired. Please log in again.". Here is my code so far:

$url = "http://localhost/joomla25/administrator/";
$cookie = "tmp/cookie".time().".txt";

$ch = curl_init();
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie);
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
curl_setopt($ch, CURLOPT_URL, $url);
ob_start(); 
$page = curl_exec ($ch);
curl_close ($ch);
unset($ch);

//get hidden inputs
preg_match_all("(<input type="hidden" name="return" value="(.*)" />)siU", $page,                     $matches1);
preg_match_all("(<input type="hidden" name="(.*)" value="1" />)iU", $page,     $matches2);
$return = trim($matches1[1][0]);
$key = trim($matches2[1][0]);

$param = 'username='.urlencode("admin")."&passwd=".urlencode("admin")."&lang=&option=com_login&task=login&return=".urlencode($return)."&".urlencode($key)."=1";

$fp = fopen($cookie,"w");
fclose($fp);

//login
$ch = curl_init();
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie);
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
curl_setopt($ch, CURLOPT_TIMEOUT, 40);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, TRUE);
curl_setopt($ch, CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT']);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);
curl_setopt($ch, CURLOPT_POST, TRUE);
curl_setopt($ch, CURLOPT_POSTFIELDS, $param);
ob_start();      
$page2 = curl_exec ($ch);
ob_end_clean();
curl_close ($ch);
unset($ch);

echo $page2;

知道出了什么问题吗?感谢帮助！