Would it be hard to replace line 55 from if (!in_array($FileExtension, $this->AllowedFileTypes[$FileType])) { to if (!in_array(strtoupper($FileExtension), $this->AllowedFileTypes[$FileType])) {
Then there is no need any more to add 9 the same extentions to the allowedfiletypes list for the same extentions but only the all uppercase version.