Downgrade PHP Version from 5.5 to 5.4 on Ubuntu 14.04

First one have to install the PPA containing PHP54:

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:ondrej/php5-oldstable
sudo apt-get update
sudo apt-get install -y php5

Then install Apache+fcgid+php5.4:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get remove --purge `dpkg -l | grep php | grep -w 5.5 | awk '{print $2}' | xargs`
sudo apt-get purge apache2 php5 libapache2-mod-php5
sudo sed -i.bak "s/trusty/precise/g" /etc/apt/sources.list
sudo apt-get update
sudo apt-get install apache2 apache2-suexec libapache2-mod-fcgid php5-cgi
sudo apt-get install php5-mysql php5-curl php5-gd php5-intl php-pear php5-imagick php5-imap php5-mcrypt php5-memcache php5-ming php5-ps php5-pspell php5-recode php5-sqlite php5-tidy php5-xmlrpc php5-xsl php5-xdebug
sudo sed -i "s/precise/trusty/g" /etc/apt/sources.list
dpkg --get-selections | egrep '^(apache|php)' | sed 's/install/hold/g' | sudo dpkg --set-selections
sudo apt-get update
sudo apt-get install  mysql-client mysql-server phpmyadmin

Note that the "switch" between trusty and precise was needed because PPA Ondrej does not have packages for trusty

Finally, continue setting up the environment as here: http://www.howtoforge.com/how-to-set-up-apache2-with-mod_fcgid-and-php5-on-ubuntu-12.04