After about a week - and of course, on the same day I post this question, I finally manage to fix this myself.
This is how I go about:
I downloaded the latest Google Client API (for php) from their github.
I added the Google folder (src) in my application/third_party folder.
Inside my controller I included the required files by doing:
require_once(BASEPATH . '../application/third_party/Google/Client.php');
require_once(BASEPATH . '../application/third_party/Google/Service/Analytics.php');
Then I added the following code below that for authorization with Service Account (which you get from the Google Console and selecting your project > APIs & auth > Credentials > Then create a new Client ID, select Service Account, when done, press "Generate new p12 key" and add that key to your third_party/Google folder:
session_start();
$client_id = '<YOUR_CLIENT_ID>'; //Client ID
$service_account_name = '<YOUR_CLIENT_EMAIL>'; //Email Address
$key_file_location = BASEPATH . '../application/third_party/Google/<YOUR KEY.p12>'; //key.p12
$client = new Google_Client();
$client->setApplicationName("ApplicationName");
$service = new Google_Service_Analytics($client);
if (isset($_SESSION['service_token'])) {
$client->setAccessToken($_SESSION['service_token']);
}
$key = file_get_contents($key_file_location);
$cred = new Google_Auth_AssertionCredentials(
$service_account_name,
array(
'https://www.googleapis.com/auth/analytics',
),
$key,
'notasecret'
);
$client->setAssertionCredentials($cred);
if($client->getAuth()->isAccessTokenExpired()) {
$client->getAuth()->refreshTokenWithAssertion($cred);
}
$_SESSION['service_token'] = $client->getAccessToken();
The code below is for getting sessions (page visits) from the last 31 days
$analytics = new Google_Service_Analytics($client);
$profileId = "ga:<YOUR_PROFILE_ID>";
$startDate = date('Y-m-d', strtotime('-31 days')); // 31 days from now
$endDate = date('Y-m-d'); // todays date
$metrics = "ga:sessions";
$optParams = array("dimensions" => "ga:date");
$results = $analytics->data_ga->get($profileId, $startDate, $endDate, $metrics, $optParams);
$data['report'] = $results->rows; //To send it to the view later
To get all the dimensions and metrics that you can use, use this link.
Example on how to send it to the view:
$this->view->load('your_view', $data);
To write it out as a chart I just used Google charts, in the JS (in the view) I just looped the data from $data['report'] to draw a chart.
Hope this will help people with this problem in the future.