I am using Ubuntu 12.10, Apache2.2, PHP-FPM. My aim is to set up a working (free) shared hosting system, that means I want to create new Linux users and jail (equals to chroot, I guess) them into their home directories so they absolutely won't have permission to touch the main file system or other users' files. I set each virtualhost's DocumentRoot to a public_html folder in the home directories.
I have already done all of this, expect jailing. I looked after the topic and I found Jailkit that looked pretty easy, but unfortunately I couldn't get it worked. I followed this tutorial but except /home/jail I used /home/tom (tom is the example user) but when I logged in as tom, I could go up to the root directory. Moreover, I set individual PHP-FPM pools to each virtualhosts for security so if you open tom.mywebsite.com and see who runs PHP ( echo `whoami`; ) it will print out tom. The other thing I set for them is open_basedir (of PHP). I don't really know what does it do and does it really counts (if I set chroot) or is it enough for now, but I set it. So the long and the short, problem is no matter if I set proftpd or other ftp programs to don't let USER going up in folders and browse, there will always be PHP where he can do it.

So the task: set chroot for each users (using Linux bash script) so don't allow them to browse other users' files and don't let them to crash system.
Thank you for your constructing comment and help in advance.