A .ctp file is not a PHP file. It is a CAKE template file. If you don't understand the difference between a .php file and a .ctp file, then you need to ask your doctor to up your anxiety medication, because you are in for some serious frustration.
Dreamweaver isn't going to work with your CAKE templates. That doesn't mean you can't create a workflow to work with both CAKE and DW. Forgive my bit of fun above, I realize you just want to do something simple. I think you are going to need to do it through CAKE.