Only notify for specified categories

Sure,

First off all, users are able to choose categories in their profile by default.

If you want to hard-code two categories in the code, it should look like this:

Line 56

if (in_array($postcats,explode(',',$user_cats[0]))) $cat_chosen = true;

should be changed to:

if (in_array($postcats,explode(',',$hard_coded_categories))) $cat_chosen = true;

You have to set $hard_coded_categories as an array of the category-ids before.

Regrads