Facebook Authorization

I developed a moderation application in php through which I moderate all posts and comments. I also have the option to post POST to the facebook fan page wall. But when I try to do this, an exception occurs that says: "The user did not allow the application to perform this action."

Any help on this !!! Thanks

Update

Here I ask permission from the user for POST through the fan page

$hasPermission = $facebook->api_client->call_method('Users.hasAppPermission',array('ext_perm'=>'publish_stream', 'uid'=>$fbuid));
        $hasPermission_offline = $facebook->api_client->call_method('Users.hasAppPermission',array('ext_perm'=>'offline_access', 'uid'=>$fbuid));

Here I am trying to post to a page wall.

$facebook->api_client->stream_publish(strip_tags(html_entity_decode($rowdata['posttext'])),$objAttachment, '', $objfbpharmawall->pageid, $uid)