Your comments

Will fix it, thank you for pointing it out.

This is not a PHP issue, but an IIS one, so phpinfo() is not of much help. If you have made the change, perhaps you didn't restart IIS.

You know that you can set a default editor for each file type, right? So that when you double-click a file, or choose "Preview", it opens with the option you want.

Neither of the two options that I mentioned prevent users from browsing folders or requires them to provide any information for access.

You can share using a link. Or, if you wish to use the main user interface for public access, a guest user account (which is still just a link).

http://blog.filerun.com/guest-users-file-sharing-simplified-2/

Step 1: Open IIS Manager

Open the Start menu and type "IIS" in to the find box. You should see an application called "Internet Information Services (IIS) Manager".

Step 2: Select your computer in the "Connections" pane

On the left, there is a "Connections" pane. You should see your computer listed here. Click on your computer name which should load the a dashboard with a handful of icons.

Step 3: Open PHP Handler Mapping

Double-click on the Handler Mappings icon to bring up the Handler Mappings screen.

Then double-click on the handler for PHP files to bring up the "Edit Module Mapping" window:

Step 4: Edit Verbs

Click on the "Request Restrictions" button, then switch to the [Verbs] tab. Switch the radio button to "All Verbs", then click "OK" to close the window, then "OK" again to close the other window.

composer require filerun/api-client:dev-master

https://github.com/filerun/api-client#installation

I recommend you to get assistance from somebody with more PHP development experience, as you won't get very far if your PHP knowledge is so limited.

Are you sure you have included the first line? (require __DIR__ . '/vendor/autoload.php';)

Having a document being converted from a binary file to a web viewing format, and loaded in a web viewer, is not going to be quicker than loading the file itself into a local viewer. The amount of data that goes from the webserver to your device is not going to be smaller.