You misunderstood the quote, the URL needs to be
http://example.com/?cat=32,33
I just tested it and it seems to work. However, the title was only one of the categories’ name, there might be other problems with this solution.
You misunderstood the quote, the URL needs to be
http://example.com/?cat=32,33
I just tested it and it seems to work. However, the title was only one of the categories’ name, there might be other problems with this solution.