Getting a file via http or evaluating a php file and getting it's output

I need to somehow merge two separate web programs written in php
together (from the user's perspective). This solution won't be
perminant, I just need something done quickly. I was thinking of two
different approches.

One would be to download a processed version (modified so it will
create validating html with the page it's being embeded in) of one of
the programs with the other, then just use print to embed it in the
page. I couldn't find out how to get a file via http here
(http://us2.php.net/manual/en/index.php). Sorry if I missed this in
the docs.

The other would be to process the other program and get it's command
line output, and print that.

If there's a better way to this, I'd be glad to hear it :)

Also, I've never written any php before; so sorry if I missed
something obvious to someone who has.