Prevent Access From Addon Domain into Upper directories

I have question to technichians.

I am interested about the hosting functionality.

For example, with 000webhost (NOT WITH CPANEL), whenever i add a new domain into my account, then absolutely separate public_html is created and a separate FTP login..

so,it means, that, even with PHP files, noone can access from one domain FTP account into another domain FTP account.

But with CPANEL, all addon domain domains are created under the same ACCOUNT PUBLIC_HTML. so, PHP programming bypasses such "ftp folders" easily.

(please, dont tell me such answers: "create a restricted ftp user, and separate restricted folder will be created under public_html" ...) I need full separate ftp areas for added domains.

well, if you dont know PHP well, dont answer me.

so, tell me what solutions you have, to make restricted such access...

It will be good, if CPANEL typical shared hostings, allowed to create different public_html 's for different domians, instead of putting them into one public_html.