Design Database schema in codeigniter

I want to make database design in codeigniter in which there are categories and nested sub categories. There are infinte categories and nested sub categories.

Category has following

  category_id – autoincremented positive int value, the primary key as well  category_name – name or level of the viewable category, the unique key  category_link – url for this category  category_status -disble etc    

Sub-category has lot of columns. User can also add columns in subcategory.
Issue is how I design for infinite nested categories and also how to manage design when user add column.

If any tutorial or info kindly share.

Filed under: php