How to fix "Call to a member function getUser()" in facebook via CodeIgniter?

It seems that you have not loaded the facebook library put this line in your construct of model file

$this->load->library('facebook', array('appId' => 'YOUR_APP_ID','secret' => 'YOUR_APP_SECRET'));

and make sure that you have put the facebook.php and base_facebook.php in libraries folder under application.

CodeHunter