How to isolate PHP apps from each other on a local machine(Windows or Linux)?

Question

For example, I use XAMPP on Windows and I have the following file structure:

C:\xampp\htdocs\website_1
C:\xampp\htdocs\website_2
C:\xampp\htdocs\website_3

By default, any script e.g. in the website_1 folder has access to any file on my computer. I want to create a "sandbox" for each website.

I tried to use open_basedir, but it significantly slows down websites.