2 sites with same folder within your hosting

Hi

I need to be able to setup several sites but only use 1 public_html folder for example:-

sitea.com ip 1.2.3.4 /home/sitea/public_html/

siteb.com ip 1.2.3.5 /home/sitea/public_html/ shared ip

sitec.com ip 1.2.3.5 /home/sitea/public_html/ shared ip

sited.com ip 1.2.3.6 /home/sitea/public_html/

The sites that have thier own ip will need to have their own SSL snd the shared will need to have shared SSL

We are trying to get Opencart multisite to work

this may give a better understanding of what i am trying to achieve
http://forum.opencart.com/viewtopic.php?t=37653

Thanks
Colin