Using multiple PHP versions

Issue :
How to install multiple versions of PHP and make one of them default? Also, how can the users choose the desired version?

Solution :
Installing and configuring concurrent PHP can be done by going to WHM -> Software -> EasyApache and when prompted for which version of PHP to run, select both PHP 4 and PHP 5. After the compile process is completed, you will be prompted for which PHP version should be default.
cPanel users can set up which version of PHP to use by going to the PHP Configuration screen in their cPanel interface. This affects all domains under their account.