Among my clients includes a website (let us refer to it as website.com). They wish to install some script an intern coded in a directory (let us say website.com/somescript).

I do not trust that script greatly and Let me make certain any file in /somescript does not need parents directory.

How do i achieve this?

Thanks!

Try open_basedir parameter which may be occur .htaccess in somescript/ directory.

When the script/directory fit in with exactly the same user(&group) then you definitely can't prevent adjusting website.com