Its obvious now, and I'm sure it can be implemented by multiselect fields.

I recommend to use the available features to be able to update K2 in the future, your suggession will make updating K2 a headache when a new version released.

The update thing is something that i think very seriously. You are absolutely right and thank you for that.

I am thinking the multiselect solution, but i find out some serious difficulties.

It seems that every item that needs more columns in extra fields, needs all extra fields to be rewritten.
Let's take an example.
We have item1, with an extra field called "Color". The "Color" is multiselect and has three values, RED, BLACK, WHITE.
If we need another item, called item2 and let's say that we need the extra field "Color", with three different values, BLUE, WHITE, GREEN.

In this case and every similar case, the administrator should create extra field "Color", assign to different group and write the values for this color.

We must consider the case that an item may have only one Color and the programming for the front end should be only once and i cannot change the php code every time they change or create a new item.

That is to say, i have to think about flexibility.

How flexible is it with your suggestion ?

P.S. Mohamed, your help is priceless. Thank you very much for your advice and your time spending.

No problem Periklis :)
I'm loving K2 and like such discussions.

Anyway, your example is very good to clarify mu proposed solution.

Please have a look at the multiselect field type and how it works.

If you have a multiselect field for the Color, its values will be all propable colors you can select for an item, so it will have RED, BLACK, WHITE, BLUE, GREEN... and so on.

For Item1 one, you will select RED, BLACK, WHITE for The Color field
For Item2 you will select BLUE, WHITE, GREEN
If any other item have only one color, you can select one color.
I don't think there will be a problem at the backend while you add/edit items.

All the tricky work will be at the frontend, and this is normal because each website has its private look&feel and its own presentation way.

When you customize the templates of K2, this will not break K2 maintainability, K2 will be updated seamlessly.

In fact the work at frontend has a lot of details and can't be disucssed here.
Anyway, I can help to complete this project for a fair cost.

You welcome anytime.

Mohamed,
your guides help me a lot and i have make some progress. But as i work in the way you propose, other problems have been arrived. Just to ask for your opinion, i try to describe what's the problem now.

Let's take an example as before and suppose that we have an extra field, multiselect and three values, 10, 20, 30.

An item has this extra field and its values with this order. 10, 20, 30.
An other item has also this extra field and the same values but with different order. 20, 10, 30.
And so on... But we can stay at this example and take another case that an item has this extra field and the values are 10, 10, 20.

Hmm, i don't know if i successfully explain these two special but not rare situations. What do you think that we can do to bypass these unpleasant situations ?

I attach a screenshot of the multiselect fields.

Hello Periklis

Realy, the case you described is a problem, because ordering of mutliselect values is not supported.

But, I think this can be handled by using text fields instead of multiselect fields, and to use a separator like "|" or "," between the values.
And the the template, you will use php explode function to display each value in a separate column.

The multiselect fields scenario allows to use these value as filters or search criteria if this is required, but You can't order them differently for each item.

You are absolutely right Mohamed.

Today morning, i thought this way out. I have some problems with the server now but i try it right away when the server comes back again...

Thanks for one more time...