FlowJS Server Side MIME Types

Question

I'm using FlowJS to handle large file uploads in a PHP application (the client doesn't want to use something like ftp), and Flow is working perfectly, with one caveat. Whenever I get a file upload, the PHP server component of flow always has the mime type listed as application/octet-stream. I'm not the first person to work on this application, and there are many features of this application that rely on the mime type for correct handling of files. Is there a way to see the actual mime type of the file on the server? I can get the mime type just fine in javascript, but I don't want to have to create some hacky work around.