use subdomain to access codeigniter's modules - php

Question

I have a sales script based on codeigniter and it's working great
I built an api for it, and am using it via: http://www.mysite/api/getdata
so I want now to access this api via a sub domain, like: http://www.api.mysite/getdata
as I think the solutions is: to redirect all *.mysite.com to mysite.com and then modify the .htaccess, but I don't know is it true?
----------------------------------------Update----------------------------------------
My current .htaccess File
<IfModule mod_rewrite.c>
# Check if mod_rewrite module loaded and we can work with SEO urls
SetEnv HTTP_MOD_REWRITE On
RewriteEngine on
# To redirect all users to access the site WITH the 'www.' prefix,
# (http://example.com/... will be redirected to http://www.example.com/...)
# adapt and uncomment the following:
# RewriteCond %{HTTP_HOST} ^yoursite\.com$ [NC]
# RewriteRule ^(.*)$ http://www.yoursite.com/$1 [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !=/favicon.ico
#RewriteRule ^(.*)$ index.php/$1 [L]
RewriteRule ^(.*)$ ./index.php [L]
</IfModule>

Answer 1

If you are using some kind of hosting service that lets you create a subdomain and point it to a document root, you can try creating a www.api.mysite domain and make the document root where mysite's /api directory is. That would get around the need to use an htaccess file. Alternatively, if you have access to your virtual host config, you can do the same thing, creating a vhost for www.api.mysite and point the document root to the /api directory.
If you don't have any control over that stuff, you'll need to setup the *.mysite.com to point to the same site as www.mysite and use an htaccess file. Something like this in the htaccess file in the document root should do the trick:
RewriteEngine On
RewriteCond %{HTTP_HOST} (www\.)?api.mysite [NC]
RewriteCond %{REQUEST_URI} !^/api/
RewriteRule ^(.*)$ /api/$1 [L]