The separation between php code and html by a template engine(for example Twig) allows the realization of sites a/o applications multi template
In this case the code is always is always the same but the output is shown in different ways. The most obvious advantage is that "logic" programming remains unique while output is managed in a specific way, even for single model. This means more rapid development and update of the application.
In this demo is used due model. Firts is developed using the framework boostrap standard, the second is developed using a theme (surcharge) called Unify.
As you can see, an equal data stored in database their display can change with a single click!