I'm not sure what your exact circumstances are but XAMPP is designed for one-person-development. It's a quick easy way to test sites locally. If you want a system wide server that all users can use, perhaps it's time to stop using it for something it wasn't designed, and is time to use a traditional LAMP stack instead.

sudo apt-get install lamp-server^

^{Note: The ^ on the end isn't a typo - it's how we denote tasks.}

That should give you a very traditional LAMP setup which you can then customise as much as you like. For service configuration, I personally like the SliceHost articles (even though I'm not a customer there) as they cover most of the basics about getting Apache, PHP and MySQL playing happily and in a nice sane way.