Facebook GRAPH api list videos from page - facebook

Question

I am trying to list all videos from a Facebook Fan Page an i got some problems. I keep getting Facebook SDK returned an error: You must provide an access token.. I tried using the access token, but no use.
CODE :
use Facebook;
use Facebook\FacebookApp;
use Facebook\FacebookRequest;
use FileUpload\FacebookFile;
use FileUpload\FacebookVideo;
use Facebook\Authentication\AccessToken;
$expires = time() + 60 * 60 * 2;
$accessToken = new Facebook\Authentication\AccessToken('mytoken1234567890', $expires);
var_dump($accessToken);
$fb = new Facebook\Facebook([
'app_id' => 'XXX',
'app_secret' => 'XXX',
'access_token' => "mytoken1234567890",
'default_graph_version' => 'v2.5',
]);
$request = $fb->request('POST', '/uniladmag/videos');
try
{
$response = $fb->getClient()->sendRequest($request);
}
catch(Facebook\Exceptions\FacebookResponseException $e)
{
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e)
{
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
$graphNode = $response->getGraphNode();
print_r($graphNode);
?>
OUTPUT :
object(Facebook\Authentication\AccessToken)#2 (2) {
["value":protected]=>
string(17) "mytoken1234567890"
["expiresAt":protected]=>
object(DateTime)#3 (3) {
["date"]=>
string(26) "2017-02-14 18:20:13.000000"
["timezone_type"]=>
int(3)
["timezone"]=>
string(13) "Europe/Berlin"
}
}
Facebook SDK returned an error: You must provide an access token.
What solutions do i have? Do i miss something?
Thanks.