PHP 4.3.11 to PHP 5

Okay, I'm a n00b here,.. and basically nu2 OS X Tiger as well. :dummy:
I have a 15" G4 Powerbook ... just a few months old.

Anyway, PHP 4.3.11 was default with the Mac I just bought.
I would like to upgrade to PHP 5.

If I get the tarball and install it as it is, does it over-ride the previously installed version?

Any help,...and/or direction for install will be greatly appreciated.
Thanks in advance!

~p

I would use the versions at http://www.entropy.ch and when you install them, they will install in two different areas and you control which is active by the httpd.conf file.