What is the best way to create files?

[eluser]shinokada[/eluser]
I am planning to create a free application for developers.

The application is a template generator.

A visitor can tick a box whatever they want to add to a template.

For example sample 1, 2, 3 and so on.
Each sample needs a html, css etc.

This application will create files and folders, one html, one css, image folder and media folder. Finally it will zip files and folders, so that a visitor can download it.

I'd like to know what is the best practice to create files.

Is there any library or helper for this purpose?

I will appreciate your suggestions.

Thanks in advance.