Users_model::generate_api_key PHP Method

    public function generate_api_key($length = 32)
    {
        $this->load->helper('security');
        $string = random_string('alnum', $length);
        $this->db->select('user_api_key')->from('users')->where('user_api_key', $string);
        $query = $this->db->get();
        if ($query->num_rows() > 0) {
            $this->generate_api_key();
        }
        $query->free_result();
        return $string;
    }