Laravel passport "Converting Authorization Codes To Access Tokens" code for codeigniter

I successfully create server and client app both using laravel, I can access data from server app to client app also. But now I want to create another client app using codeigniter. Authorization works except for the callback method. So how can I convert the this code

Route::get('/callback', function (Request $request) {
    $http = new GuzzleHttp\Client;

    $response = $http->post('http://your-app.com/oauth/token', [
        'form_params' => [
            'grant_type' => 'authorization_code',
            'client_id' => 'client-id',
            'client_secret' => 'client-secret',
            'redirect_uri' => 'http://example.com/callback',
            'code' => $request->code,
        ],
    ]);

    return json_decode((string) $response->getBody(), true);
});

into CodeIgniter 2?

Thanks

via Vandolph Reyes