I have successfully installed FilesGallery onto a Linux host where the index.php is served by an Apache2 http-server. It is indeed a super nice web app, and I did of course buy the license.

But I also wanted to have it running on my Windows 11 desktop where I have a huge photo collection, just so that I can access it conveniently at home. While you certainly can make Apache run on Windows 11, I wanted to try if I could simply serve index.php out of the IIS (Internet Information Services) web server that is built-into Windows. Turned out that it can be done, but you need to do a few tricks.

You do need to install two applications to your Windows system: PHP and FFMPEG.

This is one way how you can make FilesGallery to run under Microsoft Windows 11 IIS web server.

You could follow these instructions to enable IIS and install PHP:

install IIS
This instruction is slightly outdated such that you do not need, and indeed should not even attempt to install WinCache.

Here you can get FFMPEG binaries for Windows: link

IIS itself can be “enabled” from the Windows Control Panel, Windows Features with a few clicks, and after some time the system automatically installs everything for you. Eventually you need to reboot your computer.

Download the index.php of FilesGallery and in the beginning of the file add following:

if (!isset ($_SERVER['DOCUMENT_ROOT']) || $_SERVER['DOCUMENT_ROOT'] === '') {
    $_SERVER['DOCUMENT_ROOT'] = substr ($_SERVER['SCRIPT_FILENAME'], 0, -strlen ($_SERVER['SCRIPT_NAME']));
    putenv ('DOCUMENT_ROOT='.$_SERVER['DOCUMENT_ROOT']);
}

This tweak is needed because IIS does not pass $_SERVER['DOCUMENT_ROOT' like Apache does.

You also need to edit the absolute path to your ffmpeg.exe, as PHP served by IIS will not find it otherwise (even if it is in your PATH), for example:
'video_ffmpeg_path' => 'C:\Program Files\FFMPEG\bin\ffmpeg.exe'

Make sure that your PHP installation has required extensions enabled. For example GD is a must. That is enabled by editing php.ini, where there is a line
extension=gd

Once you have IIS installed, you can launch IIS Manager GUI to configure the web server.

In FastCGI settings you must configure the path to PHP.EXE so that IIS will serve PHP.
Test with phpinfo.php that your PHP works under IIS. It probably does not until you edit in php.ini the following setting:
cgi.force_redirect = 0
After this if you see that http://localhost/phpinfo.php works, you can continue.
Rename the “Default Web site” to FilesGallery
edit permissions of the web root document folder (as seen in Content Views, this is something like C:\inetpub\wwwroot) such that your Windows identity has full control
drop the FilesGallery index.php into the Content View of this site
in CGI, set Impersonate User to true
Set default document to index.php
In IIS Application Pools, DefaultAppPool, set Identity to your Windows identity. This allows the index.php served by IIS to write into the document folder
Link the directory containing your photos and videos to web root document folder, this way index.php will find them. Here we assume that the Windows identity you configured has at least read permissions to that directory hierarchy
Restart IIS. Now the gallery should be seen at localhost:80.

If you see something like this:

Warning: mkdir(): Permission denied in C:\inetpub\wwwroot\index.php on line 450

Then you did not set permissions correctly.

If you see this:

HTTP Error 502.2 - Bad Gateway
The specified CGI application misbehaved by not returning a complete set of HTTP headers. The headers it did return are "'"ffmpeg"' is not recognized as an internal or external command, operable program or batch file.

Then you did not configure ffmpeg path to index.php correctly.

As there are some editing that had to be done on index.php, those changes will be gone if you update it. You would need to re-edit them after an update.