PHP has built in a kind of chroot environment. It is called “basedir”. You can configure PHP scripts to access files only in specific directory similar to chroot. Basically you can configure each site to access only files located in that site directory which is a very good idea from the security point of view.

You can add the following lines to the website configuration file or to .htaccess file to enable PHP basedir:

Php_value open_basedir /var/www/foo.bar/:/usr/local/php/
This will specify that your PHP scripts can access only specified directories.