PHP code inside Ckeditor

I've read every single post regarding this but can't make it work.

I've added in my config.js:

config.protectedSource.push( /<\?[\s\S]*?\?>/g );

I'm able to write under source properly PHP code but is not executed when I load the page.

Any help is really appreciated.

I'm using the latest 3* version of Ckeditor.

Thansk