CURL登录到joomla无法正常工作

Question

我正在尝试使用curl从我的网站登录joomla网站，但我每次都失败了。 这是我的代码：

$useragent="Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.1; .NET CLR 1.1.4322; Alexa Toolbar; .NET CLR 2.0.50727)";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $urltojm); //$urltojm is url of joomla login page
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,"username=admin&passwd=".$password); //$password is my password
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 0);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
curl_setopt($ch, CURLOPT_COOKIEJAR, "COOKIE.txt"); 
curl_setopt($ch, CURLOPT_COOKIEFILE, "COOKIE.txt"); 
$buffer = curl_exec($ch);
echo $buffer;

我在这里缺少什么？