最终用户创建自定义字段和类别

I would like to get your input on the following scenario. I have Items.php page that user can view their items. they can also add custom items. What I am trying to accomplish is the following:

1. Once they create a category, a new table is create with the category as the table name and a new ID primary key in the table with the same name_id.

2. Add new fields to be associated with the category and define their type.

3. When this category is selected in a drop down, the category associated fields show up and they can add information.

So far, I was able to have the user create a new category which create a table and an ID column. I know I may be not explaining enough, but I will appreciate your input if you ever done something similar.