how to use httpd itk on centos 6.x

Run VirtualHosts under separate users

Enable the epel repository and:
yum install httpd-itk

vim /etc/httpd/conf.d/php.conf
<IfModule prefork.c>
LoadModule php5_module modules/
<IfModule worker.c>
LoadModule php5_module modules/
<IfModule itk.c>
LoadModule php5_module modules/

vim /etc/sysconfig/httpd

Add a new user without a login shell and chown your site to it

and then configure your vhost
DocumentRoot /path/to/docroot

AssignUserId desired-user desired-user

<Directory /path/to/docroot>
Options FollowSymLinks
AllowOverride None
order allow,deny
allow from all

Use different users for different sites to achieve the intended purpose.