file get contents and php code

Question

I have an engine that processes the page contents, puts them into a variable, and then prints them in a specific position within the HTML page. In the engine, I need to "embed" the code of other "static" pages that could have some PHP tags. If I use file_get_contents I will get the content as plain text if I use to include it just won't work cause it's not the function for it. So what I need is to embed the PROCESSED code into the engine.

Can someone help me with this?