Getting processed file

I'd like to be able to save the php-file that has been processed.. This without sending the processed file to the clients (user browser) in some cases.

I'll explain why I'd need it .. I'd like users to be able to submit material to my site. I would provide some functions to them which they could put in .php files, like DrawTableHeader(); or LinkTo("file.html");
These function would be stored in files I include on the server.

Now, I was planning to give them the possibility to include a number of these files in .zip archives. And when users would download them, then the files would be processed and replaced within the archive. But that shouldn't be the problem.
I just need to find a way to get the processed files before they are being sent to the browser and be able to save them to file.html or so..

Is this possible?

Perhaps I should use the file options instead.. Wouldn't be that much more trouble and will likely work.

$file_array = file("somefile.html")
and then write the info's to another using fputs() or so..