curl登录成功之后再打开新的页面是空白

//设置用户名和密码
$username = 'admin';
$password = 'admin';
//存储cookie的目录
$cookie_file = tempnam('./temp','cookie');
//form表单的处理页面
$login_url = 'http://localhost/project/discuzx2/member.php?mod=logging&action=login&loginsubmit=yes&infloat=yes&lssubmit=yes';
$post_fields = "username=$username&password=$password";

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

$url='http://localhost/project/discuzx2/index.php';
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);
curl_exec($ch);
curl_close($ch);
-----------------------------------------------------------------
我用的是diccuzx2测试的，
这是一个页面
绿色代码部分是可以登录成功的
但是加上红色代码部分就变成了空白，为什么？
实在搞不懂啊，搜也没搜到啊！大神们救命啊！

你后面好像没读取cookie文件吧

php100的第88课你去看下吧

curl_exec($ch);
curl_close($ch);

$url='http://localhost/project/discuzx2/index.php';
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 0);
curl_exec($ch);
curl_close($ch);

这样写实有问题的，你上面都关闭了这个句柄，肯定会出错