So, you upgraded to Ubuntu 10.04 but suddenly your old applications like Drupal do not work on PHP 5.3 anymore? What the hell?

Without asking why it doesn’t work because we would only loose time we want to go back to the version of PHP 5.2 where it does work! Let us list all existing PHP packages to know what version we are running:

dpkg -l | grep php

So, now we are going to duplicate the existing sources.list and replace the lucid with karmic repos and saving it in sources.list.d

sed s/lucid/karmic/g /etc/apt/sources.list | sudo tee /etc/apt/sources.list.d/karmic.list

Create a file to be a little bit ahead of our apt-get system.

sudo nano /etc/apt/preferences.d/php

And insert the following text

Package: php5
Pin: release a=karmic
Pin-Priority: 991

Let’s update the system. (You might want to do it twice to be sure)

sudo apt-get update

Installing php5 Karmic Packages. Attention! Only replace packages that were installed when doing the first command (remember the grep we did in the first step?)

sudo apt-get install php5=5.2.10.dfsg.1-2ubuntu6 php5-dev=5.2.10.dfsg.1-2ubuntu6 php-pear=5.2.10.dfsg.1-2ubuntu6 php5-cgi=5.2.10.dfsg.1-2ubuntu6 php5-cli=5.2.10.dfsg.1-2ubuntu6 php5-common=5.2.10.dfsg.1-2ubuntu6 php5-curl=5.2.10.dfsg.1-2ubuntu6 php5-gd=5.2.10.dfsg.1-2ubuntu6 php5-mcrypt=5.2.10.dfsg.1-2ubuntu6 php5-mysql=5.2.10.dfsg.1-2ubuntu6 php5-pgsql=5.2.10.dfsg.1-2ubuntu6

There you go! A fully function 5.2.10 PHP installation without troubles. If somebody knows how to make persistent so an upgrade does not replace them anymore feel free to add a comment to this post.