ummm...there are better ways to store the data .The database structure you currently have violates the First Normal Form of database design by saving category and subcategory in a single field. Here's a nice article about database normalization (Normalization
I would recommend having a Category Table and a Subcategory table , the link between the both of them being the category ID , which would be the primary key of the Category table and the foreign key of the SubCategory table.
Using such a strucure would mean that you would not need to use any parsing to get the data you want; all you would need is a simple SQL :
select c.*, sc.*
from category c, subcategory sc
where c.categoryID = sc.categoryID
and categoryID = <the category you want>
This would get you all the data related to the category you're looking for as well as all the subcategories realated to that specific category