CURL模拟登录织梦失败

[u012914916]

header("Content-type:text/html;charset=utf-8");
$url_admin = "http://localhost:202/dede";
$username = "admin";
$password = "123456";

curl_login($url_admin,$username,$password);

function curl_login($url_admin,$username,$password){
	$cookie_file = tempnam(str_replace('\\','/',dirname(__FILE__))."/cookie/",'cookie');
	$url_login = $url_admin."/login.php";
	$url_index = $url_admin."/index.php";
	$data = array(
		'gotopage' => $url_index,
		'dopost' => 'login',
		'adminstyle' => 'newdedecms',
		'userid' => $username,
		'pwd' => $password,
		'sm1' => '登录',
	);
	$ch = curl_init();
	curl_setopt($ch,CURLOPT_URL,$url_login);
	curl_setopt($ch,CURLOPT_POST,1);
	curl_setopt($ch,CURLOPT_HEADER,0);
	curl_setopt($ch,CURLOPT_RETURNTRANSFER,1); 
	curl_setopt($ch,CURLOPT_POSTFIELDS,$data);
	curl_setopt($ch,CURLOPT_COOKIEJAR,$cookie_file); 
	$res = curl_exec($ch);
	curl_close($ch);
	//echo $res;
	
	$ch = curl_init();
	curl_setopt($ch,CURLOPT_URL,$url_index);
	curl_setopt($ch,CURLOPT_POST,1);
	curl_setopt($ch,CURLOPT_HEADER,0);
	curl_setopt($ch,CURLOPT_RETURNTRANSFER,1); 
	curl_setopt($ch,CURLOPT_COOKIEFILE,$cookie_file); 
	$res = curl_exec($ch);
	curl_close($ch);
	echo $res;
}

$cookie_file这个文件里有sessionid等数据，就是登陆不上去，打印session为空。