I\'m developing one web application, using PHP eclipse IDE. For an instance i want to switch from one PHP version to another version which resides in different location.
http://gggeek.altervista.org/2007/07/21/running-multiple-php-versions-on-a-single-apache-install/
This guide is a great guide and will get you started!
Another alternative would be to install Xampp, as I believe they provide a batch file that helps you switch versions of PHP in a second.