Using Selection rules php code to show just in book pages with specific parent

Hi,
panels is amazing module!!
thanks a lot!!!
I have question:

1. If I use book module
2. I have many books
3. i want to add content (block) to all the content type "book page "
4. but I want it just to 1 specific book
5. i think that I need to use php code but I dont know how.

Please help me to solve that issue.
maybe another simple way(Contexts).
Thanks a lot.