$this->load->library('GoogleAuthenticator');

// generates the secret code
$secret = $this->googleauthenticator->createSecret();

// generates the QR code for the link the user's phone with the service
$qrCodeUrl = $this->googleauthenticator->getQRCodeGoogleUrl('Service Name', '[email protected]', $secret);

// also, you can get a code to test the service
$oneCode = $this->googleauthenticator->getCode($secret);

// get the user's phone code and the secret code that was generated, and verify
$checkResult = $this->googleauthenticator->verifyCode($secret, $code, 2); // 2 = 2*30sec clock tolerance

if ($checkResult) {
    echo 'OK';
} else {
    echo 'FAILED';
}