old/application/controllers/admin/Calendar.php

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Calendar extends MY_Controller {

	public function __construct() {
		parent::__construct();
        $this->load->model('adminModel', '', TRUE);
	}

	public function index()
    {
        if (!isset($_SESSION['user']) || empty($_SESSION['user']) || $_SESSION['user']['rank'] < 9) redirect(base_url('login'));
        $this->load->view('admin/sidebar', ['title' => 'Dashboard']);
        $this->load->view('admin/calendar');
        $this->load->view('admin/footer');
    }

    public function getAllEvents() {
        $events = $this->adminModel->getCalendarEvents();

        echo json_encode($events);
    }
}