upload video to facebook group using Graph API - facebook

Question

I'm using to GRAPH API to upload videos to my pages. I want to upload them to my groups too.
This is what I'm doing to upload video to pages and it is working.
$fb = new Facebook([
'app_id' => APP_ID,
'app_secret' => APP_SECRET,
'default_graph_version' => 'v2.2',
]);
$data = [
'title' => $title,
'description' => $description,
'source' => $fb->videoToUpload(WWW_ROOT . '../' . $path . $file),
];
try {
$result = $fb->post('/me/videos', $data, $user->access_token);
return $result;
} catch (FacebookResponseException $e) {
$response['status'] = false;
$response['message'] = 'Graph Returned an error: '. $e->getMessage();
return $response;
} catch (FacebookSDKException $e) {
$response['status'] = false;
$response['message'] = 'Facebook SDK returned an error: ' . $e->getMessage();
return $response;
}
This is working fine. But not working for group.
The problem that could be is that I don't have access_token of group and thus using user's access_token
How to get access_token?
To get access token of pages, I am doing
try {
$userPages = $fb->get('/me/accounts', $accessToken->getValue());
$userPages = $userPages->getDecodedBody()['data'];
} catch (FacebookResponseException $e) {
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch (FacebookSDKException $e) {
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
which return an array of pages with id, name, category and access_token.
[
0 => [
'name' => 'my page name',
'category' => 'Education',
'id' => 1234567890,
'access_token' => 'hkjh3k42j4j4l1kj4h1lj'
],
]
But when I get groups using
try {
$userGroups = $fb->get('me/groups', $accessToken->getValue());
$userGroups = $userGroups->getDecodedBody()['data'];
} catch (FacebookResponseException $e) {
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch (FacebookSDKException $e) {
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
I only returns
[
0 => [
'name' => 'my group name',
'privacy' => 'OPEN',
'id' => 1234567890
]
]
and there is no access token.
How can I get access token of the group?
Here $accessToken->getValue() is the access_token of user when he authenticates the app.