Question

How can I completely uninstall php 5.3

I would like to have 5.2.10 instead of.

When I do php -v
PHP 5.3.4 (cli) (built: Dec 28 2010 17:00:24)
Copyright (c) 1997-2010 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies

Answer 1

How did you end up with such a recent version of php in this old version of Ubuntu? You could upgrade to Karmic (9.10) that includes php 5.2.10 (http://packages.ubuntu.com/search?keywords=php5&searchon=names&suite=all&section=all)

Otherwise:
Set up apt-pinning to allow installing packages from the karmic repository as well. First, add the karmic repositories in etc/apt/sources.list (it’s the same as your current repositories, just copy them and replace the release name). Then edit /etc/apt/preferences :
For example this should work:

Package: *
Pin: release a=(9.04 name)
pin-Priority: 700

Package: *
pin: release a=karmic
Pin-Priority: 500

Remove any php packages installed (using synaptic). Then you can do:

apt-get install -t karmic (php pagkages)

But be careful with any dependancies of php in order not to break something else in your system.