Displaying files

I think this should be a simple question and answer, but after looking through the manual and goggling I have yet to find an answer. Question: Using PHP, how would I go about opening a file in a window, table or div? Example: I have a file called 123.xls. When a condition is met, I want PHP to open this file into the current window. I know I can use Javascript to easily do this, but due to the requirements of my application, javascript is not an option here. I tried using fopen() but that only opens the file in the background for PHP to read/write to and will not display the file in a browser. Any ideas? Thx, Dan