Downgrade or install php 5.2.x on Ubuntu 10.x

http://2bits.com/drupal-planet/various-ways-running-php-52-ubuntu-1004-l... -
(Approach 3)

If you have the package "python-software-properties installed, you can easily add the repository using the command:

add-apt-repository ppa:txwikinger/php5.2

That will install the GPG key for security verification.

If you are using apt-get, then you need to create a file called /etc/apt/preferences.d/php for pinning the versions, so they remain at 5.2 and don't get upgraded to 5.3 when you run apt-get to upgrade your installation.

Put this in the file:

Package: libapache2-mod-php5
Pin: version 5.2.10*
Pin-Priority: 991

Package: libapache2-mod-php5filter
Pin: version 5.2.10*
Pin-Priority: 991

Package: php-pear
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-cgi
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-cli
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-common
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-curl
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-dbg
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-dev
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-gd
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-gmp
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-ldap
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-mhash
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-mysql
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-odbc
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-pgsql
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-pspell
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-recode
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-snmp
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-sqlite
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-sybase
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-tidy
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-xmlrpc
Pin: version 5.2.10*
Pin-Priority: 991

Package: php5-xsl
Pin: version 5.2.10*
Pin-Priority: 991

Then you do "apt-get update" and the right packages are either pulled in due to installing them directly or indirectly through dependencies.

Other Method (sometimes errors)

# remove all php packge
sudo aptitude purge `dpkg -l | grep php| awk '{print $2}' |tr "\n" " "`

sudo su

# use karmik for php pakage
echo -e "Package: php5\nPin: release a=karmic\nPin-Priority: 991\n" >> /etc/apt/preferences.d/php

apt-cache search php5-|grep php5-|awk '{print "Package:", $1,"\nPin: release a=karmic\nPin-Priority: 991\n"}' >> /etc/apt/preferences.d/php

apt-cache search -n libapache2-mod-php5 |awk '{print "Package:", $1,"\nPin: release a=karmic\nPin-Priority: 991\n"}' >> /etc/apt/preferences.d/php

exit

# add karmik to source list
sed s/lucid/karmic/g /etc/apt/sources.list | sudo tee -a /etc/apt/sources.list.d/karmic.list

# update package database (use apt-get if aptitude crash)
sudo apt-get update

# install php
sudo apt-get install -t karmic php5-cli libapache2-mod-php5