Thanks for all the testing you are doing. I don't run into any of these issues even though I uninstall and re install before I zip up the finished module. I'm also using a Linux web server to do my tests and most PHP plug-in are already installed.
exif_imagetype() is a PHP function to test image type. Mazarin if you're not seeing an error relating to this, your server already has it enabled.
checkPermissions: I'm not sure why my didn't see this in my tests, but try adding the following to the top of index.php
include_once "include/functions.php";
Undefined offset on line 792. I'll have to look into this more and try installing a version of XOOPS in a sub directory.
I am using XOOPS version 2.4.0
Optikool