Like many devs, I do not want to allow any PHP input via the UI. I've gone as far as to remove php.module entirely to ensure that even admins can not turn on PHP. This is a common requirement for any mass hosting solutions that want to give user 1 access to their users. What I'd like is for custom breadcrumbs to check module_exists() for php.module before displaying the option to enter php into the configuration form. If I'm not mistaken other contrib modules are using php.module as a kill switch of sorts.