Multisite with codeigniter HMVC

Really depends if they are running independently of each other as khalilhimura suggested you can just load different application folders per domain.

Or if you are doing a multi-site system that will grow dynamically, you can store the domain in the database table with the site information and look that up to get site information (make sure you index the domain field).  All your tables will need a site_id of some sort to look up information.

Something like below in model will let you look up.

PHP Code:

function site_lookup()
    {
        $domain = strtolower($_SERVER['HTTP_HOST']);
        $domain = explode('.', $domain);
        $domain = array_reverse($domain);
        
        $this->db->select('*');
        $this->db->from('sites');
        if(isset($domain[2]))
        {
            $this->db->where('site.domain', $domain[2].".".$domain[1].".".$domain[0]);
        } else {
            $this->db->where('site.domain', "www.".$domain[1].".".$domain[0]);
        }
        $this->db->limit(1);
        return $this->db->get();
        
    }