invalid api keys permission denied error in google api using php - php

Question

I am using google api first time my code execute perfectly even give me data using people service api...but second time it give me following error
Type: Google_Service_Exception
Message: { "error": { "code": 403, "message": "The request is missing
a valid API key.", "errors": [ { "message": "The request is missing a
valid API key.", "domain": "global", "reason": "forbidden" } ],
"status": "PERMISSION_DENIED" } }
i am using codeignitor and this is redirected uri controller function...thanks in advance and sorry for poor english..
$client = $this->google_client_setup();
$client->authenticate($this->input->get('code'));
$access_token = $client->getAccessToken();
$people_service = new Google_Service_PeopleService($client);
$profile = $people_service->people->get(
'people/me', array('personFields' => 'names,emailAddresses'));
$access_token = $access_token['access_token'];
$email = $profile['emailAddresses'][0]['value'];
$name = $profile['names'][0]['displayName'];
$user = [
'email' => $email,
'name' => $name,
'is_admin' => 0
];

Answer 1

It's hard to tell, but I would think that if it says it's missing valid api key, you should treat that as answer ;)
Are you being redirected somewhere after first run? That could explain problem Javier commented on.
I'd suggest to dump two things to debug the code:
$this->input->get('code')
and if this is ok, then
$access_token
this should give you idea what your problem is :)
Good luck!