This solution is Only for local system / localhost on windows:
The simplest way to install xampp 5.6.X version as per your requirement in other windows drive then run xampp 5.6.X services from it's control panel for php 5.6 version.
NOTE: If you already have xampp (any other version) on your system then please close that xampp's services then start xampp 5.6.x services otherwise this solution will not work.
You can download your required (xampp 5.6 as per question) xampp version from below link:
https://sourceforge.net/projects/xampp/files/XAMPP%20Windows/
I have used this solution many times, it worked like charm. I hope this will also help you. Thank you to ask this question.