PHP docs work within the browser just like a regular HTML document.
This really depends on how your framesets and script are setup. If the scripts display the info immediatly upon displaying the framed page, then simply use the script url in your frameset, as if it were a regular HTML document. If the surfer must first click a link, and then the script displays the message, again just like a regular HTML documant, use the proper target.
<A HREF='myscript.php' TARGET='left'>
Don't let the fact that they are PHP docs confuse you. When it comes to displaying the output, targettting windows, ect, they react just like HTML documents.
You cannot dictate through the script which window it is displayed in, you must do that from the HTML outputted from the scripts.