The default Yum repositories currently contain PHP 5.1.3 which is, of course, too old for our needs. So we are going to need to add another repository.
Atomicorp, the makers of Atomic Secured Linux host a repository containing the information we need. They have instructions on how to install the repository here, but we are going to pursue a slightly more secure method (Note: It is never wise to pipe the output of wget straight to the shell!).
To begin, you will need Shell access to your server. The most common method of obtaining this is to use Secure Shell (SSH), however some control panels such as Plesk will allow you to obtain this access from within your browser.
wget -q -O installer.sh "http://www.atomicorp.com/installers/atomic"
The last command will allow you to view the contents of the downloaded file, have a quick look over just to see if there's anything suspicious! At time of writing, running the md5sum command should give the following result (this will change if they update the script)
Now having verified the script, we can execute it and perform the upgrade
yum upgrade # Follow the instructions
service httpd restart # Restart the HTTP Daemon (usually Apache)
If all went well you should now be running PHP 5.3! The process will take a while as there may be quite a number of packages that need updating once the new repository has been installed. Future updates should be far less painful however, simply requiring
yum upgrade packagename #e.g. yum upgrade php
Virya Technologies can provide support if you encounter problems or simply feel that you'd like someone else to perform the upgrade for you