I tried to make this tool as easy as possible to use. However, it does require some instructions. First and foremost, this isn't perfect. The only way to know if it will work is to test it on your own forum. This is my disclaimer: I make no guarantee or warranty that this will work or won't break your forum. That being said, whatever you put in to this is what you'll get out of it. This tool requires Javascript. If you don't have it enabled, you won't get anything out of it.
That brings me to the next point. If you want to do an empty string, you have to put that empty string (with quotes) in the form field. In order to support PHP, you need to enclose your strings in quotes. See the examples (default tags) to understand that better. If you leave a field blank, it won't appear in the end result. You do not have to add commas at the end. Several fields will always appear: type, tag, length, block_level, and autolink. I tried to add as many safeguards as possible. There are a lot of rules for the BBC parser that I have attempted to add in here.
So, how do you use it? You can select a default tag and make changes to that or you can start with your own. Start by selecting the appropriate type (it will hide/show fields). Then put what you want in each of the fields. When you're done, see the results. Just copy them to your application.