，关于curl模拟登陆

高手进，关于curl模拟登陆
模拟登陆织梦，版本5.7，已经去掉后台验证码，不知道为啥一直登陆不上（提示登陆成功却又跳回登陆地址）

<?php
$cookie_file    =    tempnam('./temp','cookie');
$login_url        =    'http://localhost/dedecms/dede/login.php';
$post_fields    =    'gotopage=%2Fdedecms%2Fdede%2Findex.php&dopost=login&adminstyle=newdedecms&userid=admin&pwd=123456&sm1=';

$ch = curl_init($login_url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,0);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_fields);
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie_file);
curl_exec($ch);
curl_close($ch);


$url='http://localhost/dedecms/dede/article_add.php?channelid=1';
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie_file);
$contents = curl_exec($ch);


curl_close($ch);
?>

------解决方案--------------------
dede登陆类做了限制