This small article tell you how to disable open_basedir protection in your plesk server. For example you own a domain say foo.com in your plesk server. Then do the following steps,
1) Create a vhost.conf as follows,
2) Now edit this vhost.conf and add the following lines.
php_admin_value open_basedir none
3) Now tell psa to reconfigure httpd settings and restart httpd
/usr/local/psa/admin/sbin/websrvmng -v -a
Now you can create a phpinfo page and test it .