WARNING, it is not recommend to do this !!!
you can edit the php.ini file for the user,
for php-fcgi it is:
/var/www/fcgi/THEDOMAINYOUWANT.TLD/php5/php.ini
and add additional directories to open_basedir. e.g. /var/www or if you are crazy only /
EDIT:
in your case, use /var/www/virtual