I am looking same like a Visual Studio IDE for Comparing the latest document changes. refer image
But Visual studio did not support PHP. So I am looking same functionality in any IDE which is suitable for Xampp and WordPress.
You can open PHP files in VS, and I expect the comparison function will still work.
However, and generic text comparison approach is to use Notepad++ with the Compare plugin:
http://www.technicaloverload.com/compare-two-files-using-notepad/
If you want a PHP IDE, Eclipse will allow you to compare files too (Compare With Other Resource function):
https://www.eclipse.org/downloads/packages/release/2018-09/r/eclipse-ide-php-developers