facebook, post comment via php curl

From one tutorials here:

Post a reply on a comment in Facebook using cURL PHP / Graph API

I tried to post comment to after one post, But return:

[type] => OAuthException [message] => (#200) The user hasn't authorized the application to perform this action

This is not my app acount wall's post id, I tried to my freinds wall, he have allowed my app, I can post a post to his wall, but failed in a comment, I got the post id via https://graph.facebook.com/<his fid>/feed?access_token=140开发者_如何学JAVAXXXXXXXXXXX, so the post id has no problem.

What steps have I missed?

$fbId = '100001102789652_233997699980321';
$accessToken = '140XXXXXXXXXXXX';
$url = "https://graph.facebook.com/{$fbId}/comments";

$attachment =  array(
        'access_token'  => $accessToken,
        'message'       => "Hi comment",
);

// set the target url
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $attachment);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$comment = curl_exec($ch);
curl_close ($ch);
$comment = json_decode($comment, TRUE);
print_r($comment);

?>

---

curl_setopt($ch, CURLOPT_POSTFIELDS, $attachment);

should be

curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($attachment));

as you can't post an array