security - How can I relax PHP's open_basedir restriction?

open_basedir limits the files that can be opened by PHP within a directory-tree.

I am storing several class libraries and configuration files outside of my web root directory. This way the web server does not make them publicly accessible. However when I try to include them from my application I get an open_basedir restriction error like this:

Warning: realpath()
[function.realpath]: open_basedir
restriction in effect.
File(/var/www/vhosts/domain.tld/zend/application)

is not within the allowed path(s):
(/var/www/vhosts/domain.tld/httpdocs:/tmp)
in
/var/www/vhosts/domain.tld/httpdocs/index.php
on line 5

My web root is here:

/var/www/vhosts/domain.tld/httpdocs

My libraries and configuration directory are here:

/var/www/vhosts/domain.tld/zend

What would be the best workaround to relax the open_basedir restriction so that the the directory tree under the domain folder becomes available to my application? I have a number of domains that I want to do this with, and I'm also obviously wary of creating security vulnerabilities.

Note: I am using CentOS, Apache, Plesk, and I have root ssh access to the server. And though this doesn't apply to Zend Framework directly, I am using it in this instance. So here is the inclusion from Zend's bootstrap:

define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../zend/application/'));
set_include_path(APPLICATION_PATH . '/../zend/library' . PATH_SEPARATOR . get_include_path());

Answer

You can also do this easily on a per-directory basis using the Apache (assuming this is your web server) configuration file (e.g. httpd.conf)

php_admin_value open_basedir "/var/www/vhosts/domain.tld/httpdocs:/var/www/vhosts/domain.tld/zend"

you can also completely remove the restriction with

php_admin_value open_basedir none