Dealing with Sessions

[eluser]mulama77[/eluser]
i came across this lines of code

$params['client_id'] = Session::get('client_id');

which when running produces

Fatal error: Class 'Session' not found in C:\xampp\htdocs\myapi\application\controllers\oauth.php on line 34

The initial tutorial does not have a class called Session. Is the above line of code same as

$params['client_id'] = $this->session->get('client_id');

which also produces

Fatal error: Call to a member function get() on a non-object in C:\xampp\htdocs\myapi\application\controllers\oauth.php on line 27

or what should i do to to make the first line of code work because when i run

$params['client_id'] = $this->get('client_id');

it works but the author insisted the use of sessions.