how do you switch PHP versions?

[higuy]

I installed XAMPP 1.7.2 on my Ubuntu 9.04. I'm attempting to install Joomla! and it can't use PHP 5.3

I installed PHP 5.2.9 to the directory /opt/lampp/bin

Now I can't figure out how to switch to PHP 5.2.9

I found a tutorial on how to do it in XAMPP for Windows, so I'm assuming it can be done in XAMPP for Linux.