Intranet applications are programs that are only made available to a closed group of users in the local network. The display often occurs in a browser, e.g. Firefox, Edge, Chrome. The presentation of the application is like a web page, however, the contents do not come from outside, but from the company's own server.

An advantage of an intranet application in the browser is that multiple users can work with the same database simultaneously. Additionally, the program doesn't need to be installed on every computer and it's independent of the operating system, i.e. it runs on Windows, Mac, Linux, possibly a tablet/pad or smartphone. And in case of a program update, it's sufficient to install the new version once on the central server.

If the server has a Windows operating system, you can use the IIS (Internet Information Services) that comes with Windows as web server software, see below. On Linux, however, NGINX or Apache HTTP Server are usually used.
The following sections are a guide to activating IIS on Windows and setting up PHP.

In the realm of internet and intranet, PHP is the most widely used programming language that runs on the server and is particularly used for generating dynamic web pages. 78 % of all websites use PHP (as of 2024).

The IIS (Internet Information Services) are part of Windows. If you activate IIS in the settings, Windows takes care of the installation and updates.

Menus in Windows 10 ...
Click on the Start menu > Settings > Apps
> at the very bottom: Programs and Features
> in the next window: Turn Windows features on or off
> select: Internet Information Services

You should also activate the following:
World Wide Web Services > Security > URL Authorization

Download PHP for Windows from php.net, at
https://windows.php.net/download.
There is no installer, but a .ZIP file. Take the NTS version (Non-Thread Safe), which is recommended for Windows IIS.

Unpack the ZIP file into a new folder whose name (and entire path) must not contain any spaces. The documentation therefore suggests the folder C:\PHP\.

Finally, IIS needs to be told where to find the PHP folder. To do this, open the IIS Manager by right-clicking on the Windows Start menu, selecting 'Run' and entering "inetmgr" there.

The management program opens.
Click on your computer name in the left area. Then select "Handler Mappings" in the middle area. In the right area, select: "Add Module Mapping".

To test if PHP and the IIS web server are working together correctly, you need a .php file that is stored in the web root. Create, for example, a file "phpinfo.php" with the following content:

<?php
  phpinfo();
?>

In the Apache web server, it is common to have a configuration file named ".htaccess" stored in individual folders, which controls what properties the folder has.
For Windows IIS, however, an XML file named "web.config" must be saved in the respective folder to configure it individually.

"web.config" file to block access from outside ... (the following corresponds to "deny from all" in an .htaccess file)

<configuration>
  <system.webServer>
    <security>
      <authorization>
        <remove users="*" roles="" verbs="" />
        <add accessType="Deny" users="*" />
      </authorization>
    </security>
  </system.webServer>
</configuration>

<configuration>
  <system.webServer>
    <defaultDocument>
      <files>
        <clear />
        <add value="index.php" />
      </files>
    </defaultDocument>
  </system.webServer>
</configuration>

When I tried out a locally stored webpage, I noticed that some images weren't displayed. These images are stored in the fairly new .webp file format. In this case, it seems IIS hadn't yet been set by default to serve .webp files. This needs to be manually added if needed.

Data transmission in the local intranet is typically rarely encrypted using SSL (https), because you need to deal with self-signed certificates for that. Nevertheless, it's likely that you'll need OpenSSL as an extension for PHP, as there are a few PHP functions that use OpenSSL, e.g. the hash function openssl_digest(), random numbers using openssl_random_pseudo_bytes() or other encryptions with openssl_encrypt() and openssl_decrypt().

Conveniently, PHP comes with the OpenSSL extension, but it's not activated by default. Open the "php.ini" file in the PHP folder by right-clicking and selecting "Edit". If you need administrator rights to write in your PHP folder (recommended), you must first start the editor "as administrator" and then load the file in it.

;extension=openssl

;extension_dir = "ext"