How do i downgrade PHP 5.5.9 to PHP 5.4.29 on a new Ubuntu 14.01

Downgrading isn’t really a supported option. PHP 5.5.9 is the only version shipped with Ubuntu 14.04. To downgrade you’d need to purge PHP from the system and then install a version from an older Ubuntu release. You’d then get into problems with the various other bits in the PHP ecosystem that are available for Ubuntu 14.04 are targeting PHP 5.5.x. <br> <br>If you really need PHP 5.4.x, I suggest using the Debian 7.0 image as your base. That ships with PHP 5.4.4 along with various backported security fixes. It would be much easier to set up a LEMP stack on Debian 7 than to downgrade PHP on Ubuntu 14.04 Check out this article: <br> <br>https://www.digitalocean.com/community/articles/how-to-install-linux-nginx-mysql-php-lemp-stack-on-debian-7

Its not that easy to downgrade php in ubuntu 14. But its easier to install PHP 5.4 parallel to PHP 5.5 uing phpfarm. You can download PHP 5.4, compile it and configure Apache with fastCGI:

http://www.jabommi.de/wiki/downgrade-php-5-5-to-5-3-ubuntu-14-with-multiple-php-versions/

As an option, you can alternatively install Ubuntu 12.05 LTS and then php 5.4 by following, for example, this tutorial:

http://tecadmin.net/install-apache2-mysql-php5-on-ubuntu-systems/