Added helper file with session related functions.

application/helpers/session_helper.php

@@ -0,0 +1,60 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        http://easyappointments.org
+ * @since       v1.3.0
+ * ---------------------------------------------------------------------------- */
+
+if ( ! function_exists('session'))
+{
+    /**
+     * Get / set the specified session value.
+     *
+     * If an array is passed as the key, we will assume you want to set an array of values.
+     *
+     * Example "Get":
+     *
+     * $logged_in = session('logged_in', FALSE);
+     *
+     * Example "Set":
+     *
+     * session(['logged_in' => FALSE]);
+     *
+     * @param array|string $key
+     * @param mixed $default
+     *
+     * @return mixed|NULL Returns the configuration value or NULL if setting the configuration key.
+     *
+     * @throws InvalidArgumentException
+     */
+    function session($key = NULL, $default = NULL)
+    {
+        /** @var EA_Controller $CI */
+        $CI = &get_instance();
+
+        if (empty($key))
+        {
+            throw new InvalidArgumentException('The $key argument cannot be empty.');
+        }
+
+        if (is_array($key))
+        {
+            foreach ($key as $item => $value)
+            {
+                $CI->session->set_userdata($item, $value);
+            }
+
+            return NULL;
+        }
+
+        $value = $CI->session->userdata($key);
+
+        return $value ?? $default;
+    }
+}