Try to use Frames. You can put the doc inside a FRAMESET with one hidden frame:
<FRAMESET ROWS="0,*">
<FRAME SRC="none.html" NAME="nonVisibeFrame">
<FRAME SRC="index.php" NAME="VisibleFrame">
</FRAMESET>
This way, the user wouldn't see the URL in the bar, because they would be navigating inside the FRAMESET. Nonetheless, if they look at the page properties, they will se the real URL, and can type them in the bar.
This solution is not the best, but it's cheap and works (at least with the normal non-programmer user)
fLIPIS