OAuth.io server-side doesn't refresh Google token - php

Question

At first please do not mark this as duplicated as this is related to server-side (PHP) and not to client-side as other posts.
I'm trying to refresh the token for Google API through Oauth.io. I followed this and many other posts but no luck. Unfortunately Oauth.io documentation is not the best one. I don't have this problem with Twitter and Facebook only Google.
I'm getting refresh_token when I connect for the first time. Then I need to do API call once a day.
{
"access_token":"xxx",
"token_type":"Bearer",
"expires_in":3600,
"refresh_token":"xxx",
"id_token":"xxx",
"provider":"google_analytics"
}
The question is how to refresh Google token through Oauth.io?
The documentation says:
// The auth method automatically refreshes the tokens if needed
$request_object = $oauth->auth('facebook', array(
'credentials' => $credentials
));
and points here, but it doesn't solve the problem. All it does is that I'm getting refresh_token value in response.
UPDATE
According to this post I tried to do:
$request_object->post('https://oauth.io/auth/access_token', array(
'code' => 'xxx', // here I tried access_token, refresh_token
'key' => 'xxx',
'secret' => 'xxx',
));
but all I'm getting is
array(4) {
'status' =>
string(5) "error"
'code' =>
int(401)
'message' =>
string(70) "Bearer token invalid. Follow the oauth2-token link to get a valid one!"
'data' =>
array(1) {
'code' =>
string(17) "UnauthorizedError"
}
}
Still nothing.

Answer 1

Finally I found it. You can refresh the access_token using:
$this->oauth = new OAuth();
$this->oauth->initialize($publicKey, $secretKey);
$refreshedCredentials = $this->oauth->refreshCredentials($oldCredentials, true);
or
$request_object = $oauth->auth('google_analytics', array(
'credentials' => $credentials,
'force_refresh' => true
));
Both answers can be found here. I had it in front of all day long and did not see it.
I prefer using 1st solution as I want to save new access_token so I can reuse it later. And you need to remember that you need to pass refresh_token, which you got with first access_token, along with last access_token to get refreshed access_token - refresh_token doesn't change until user revoke access.