How to use condtional validation in cakephp 3 ?If checkbox checked validate fields?

[naidim]

Conditional Validation in Cake is in the book: https://book.cakephp.org/3.0/en/core-libraries/validation.html#conditional-validation

Also my tutorial with an example of its use: http://www.naidim.org/cakephp-3-tutorial-21-conditional-validation