facebook fan page wall post via php - php

Question

I am using php-sdk-4 for facebook wall posting using my app credential. Everything is working fine. Problem is only posting on user facebook wall or through user post on his facebook fan page wall working but when I used his facebook fan page secret code for publish a post on facebook fan wall then show me error :-
(#200) The user hasn't authorized the application to perform this action
My facebook app in testing mode
I am doing all these steps as admin.
In my project I want functionality user come login through facebook and select his facebook fan page and publish some text or image on his facebook fan page
Code :-
$facebook = new Facebook(array(
'app_id'=>'XXXXXXXXXX',
'app_secret'=>'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
'default_graph_version' => 'v2.5'
));
$graph_url_pages = "https://graph.facebook.com/me/accounts?access_token=".$accessToken;
$pages = json_decode(file_get_contents($graph_url_pages)); // get all pages information from above url.
for($i=0;$i<count($pages->data);$i++)
{
$page_token = $pages->data[$i]->access_token;
$pageId = $pages->data[$i]->id;
$params = array(
'access_token' => $page_token,
'from' => 'XXXXXXXXXXX',
'to' => $pageId,
'message' => 'Google Inc',
'link' => 'http://www.google.com/',
);
try {
$response = $facebook->post('/'.$pageId.'/feed', $params);
} catch(Facebook\Exceptions\FacebookResponseException $e) {
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
$graphNode = $response->getGraphNode();
print_r($graphNode);die;
}
In code when I passed access_token then show me error but when I passed $accessToken (user access token) then user post going on facebook fan page wall but I want facebook fan page publish a post on timeline.