Help with server setup

Hello everyone, I have created a multiple applications inside of  codeingiter which share the common system folder by following the guide in Code Igniter documentation.
The setup is as follows (I have removed the application and system folder outside the public_html as I have read it provides security)
codeigniter/
application/
project1/
project2
system/
webroot/
index.php  -Points to project1
project2.php  --Points to project2

I am able to call my applications in the following way
example.com
example.com/project2.php
Now the problem is that I want to setup these on a server as the following Urls.
example.com
project2.example.com
How can I achieve this ...I am a newbie to codeigniter..