There are many people looking for a solution on how to downgrade their php version  from 5.3.x and greater back to php 5.2.x in linux server when plesk was installed. Actually the downgrade does not looks difficult but just need to follow the steps below:

1) First, you have to remove all your php and dependencies that have been installed in the server such as yum remove php php-cli php-common.

2) Once it’s done, your plesk will broken, but that’s fine and no worry. What you need to do is try to check out your yum list whether got any php 5.2.xx version by using command yum list | grep php.

3) If there has no php 5.2.xx version available in your yum list, then you will need to add it into your yum repo by using the following command: wget -q -O – http://www.atomicorp.com/installers/atomic | sh

4) Once it’s installed, you have to make sure php 5.3.xx version and mysql 5.5 version are excluded from the list by adding command below into /etc/yum.conf:

exclude=php*5.3* mysql*5.5*

5) Once done, you can try to check the yum list again and you should be able to see php 5.2.xx to be available in the list.

6) Once the preparation was done, it’s time for us to do the re-installation for plesk by download the autoinstaller from plesk official website. Do remember to put –all-version at the end of the line when you try to run the installer, this is to make sure you will be able to install back your existing plesk version.

7) You can just follow the step of plesk installation and complete it.

8) Once completed, you will be able to see you are running plesk in php version 5.2.xx now! Cheers!

PS: Please backup all your data before you downgrade your php version in plesk.