CodeIgniter with multiple subdomains

As per your requirement you need to added a unique field for subdomain. And another option for you, you can make multiple tables as per subdomain for manage the content as per subdomain.

That said my solution, for those who may stumble across it is, in the routes.php I ended up making a small function to get the HTTP_HOST split it up based on . and use it from there to my needs. My example is as follows.

Mind you I also replaced everything in the routes.php so its not just a straight line of $route['this/that'] = 'dir/controller';

Code:
<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/*

| -------------------------------------------------------------------------

| URI ROUTING

| -------------------------------------------------------------------------

| This file lets you re-map URI requests to specific controller functions.

|

| Typically there is a one-to-one relationship between a URL string

| and its corresponding controller class/method. The segments in a

| URL normally follow this pattern:

|

|   example.com/class/method/id/

|

| In some instances, however, you may want to remap this relationship

| so that a different class/function is called than the one

| corresponding to the URL.

|

| Please see the user guide for complete details:

|

|   http://codeigniter.com/user_guide/general/routing.html

|

| -------------------------------------------------------------------------

| RESERVED ROUTES

| -------------------------------------------------------------------------

|

| There area two reserved routes:

|

|   $route['default_controller'] = 'welcome';

|

| This route indicates which controller class should be loaded if the

| URI contains no data. In the above example, the "welcome" class

| would be loaded.

|

|   $route['404_override'] = 'errors/page_missing';

|

| This route will tell the Router what URI segments to use if those provided

| in the URL cannot be matched to a valid route.

|

*/

function whichSubRoute()

{

    $subs = array(

                "api"=>"api/",

                "m"=>"m/"

                );

    $curr = $_SERVER['HTTP_HOST'];

    $curr = explode('.', $curr);

    if(array_key_exists($curr[0], $subs))

    {

        return array($curr[0], $subs[$curr[0]]);

    }

    return false;

}

//due to the the way this setup works, some controller references

//can be found multiple times (and in no particular order).

//also note due to this setup, each method has its own default and 404

$choiceRoute = whichSubRoute();

if($choiceRoute !== false)

{

    if($choiceRoute[0]=="api")

    {

        $route['default_controller'] = "welcome";

        $route['404_override'] = '';

        //start version 1 (mvp API)

        $route['1.0/user/(:any)'] = $choiceRoute[1].'v1_userinfo/index/$1';

        //controllers outside of "/api"

    }

    if($choiceRoute[0]=="m")

    {

        $route['default_controller'] = "welcome";

        $route['404_override'] = '';

        //start version 1 (mobile)

        $route['welcome']                   = $choiceRoute[1].'m_welcome';

        $route['dashboard']                 = $choiceRoute[1].'m_dashboard';

        $route['user/(:any)']               = $choiceRoute[1].'m_userinfo/index/$1';

        $route['reg']                       = 

        //controllers outside of "/m"

        $route['login/auth']                = 'login/auth';

        $route['logout/mobile']             = 'logout/mobile';

        //end version 1 (mobile)

    }

}

else

{

    $route['default_controller'] = "welcome";

    $route['404_override'] = '';

}

/* End of file routes.php */

/* Location: ./application/config/routes.php */