Better way to handle, step by step application

I'm a newbie in PHP and I have to do an application that manage different steps but I don't know how to handle it.

I don't really know how to explain this in english (my title probably doesn't mean what I want to say), but the point is that a user seize a number, and following the number seized, different operations can be done.

And for each step, following the choice of the user, something different can happen.

User can have multiple choice, which will result some different result.

But also, it is possible that 2 operations return the "same" result, with different information.

For example if the point is to describe a product, if we have a car and a swimming pool, a car will not have the same information at the beginning, but the point is to take all information to show it the same way as a pool (as all other products). We will certainly have some common points but a pool doesn't have wheels or whatever.

A picture is worth a thousand words (and even more in this case), I tried to make a diagram which shows how it appears :

Also, I use MVC pattern and have to use AJAX from step 1 to final step.