Confirming uploaded file type

[HaLo2FrEeEk]

Hey, I have an upload script that I need to be only able to upload two different file types, ppf and sppf, the mime type of which is application/ovtet-stream.  I cannot find a suitable header or footer consistent in all the files, is there any way I can still verify that the files being uploaded are in fact either sppf or ppf, and not simply a renamed exe or some other file?  Perhaps a process of elimination, like checking to see whether it does not have the headers you would expect in other files of the mime type application/octet-stream?  Can someone please help me?

[MadTechie]

what are (s)ppf files ? what program uses them ?

[HaLo2FrEeEk]

They are mods for Halo 2, patches that you apply to the map to mod it.  There really aren't any official programs that use it, but dotHalo and entity, as well as the ppfinator and sppfinator.

[MadTechie]

only thing i could think of is find something incommon with the files to check for  :-\

ie is the first 4k always the same (excluding a few bytes in fixed positions)

[HaLo2FrEeEk]

Well, I tried that, but there doesn't seem to be anything like that.  There is a header about windows media audio and such, but I figured that is in all wma's too, so people could upload those.