function call by getting the name of function from URL

[eluser]alberta[/eluser]
can you tell me how to do this using sessions.

suppose this is url

Code:

http://localhost/project/index.php/projects/site_plan

here site plan is name of function.

Now i want to call "this-site_plan();" in index() function how ll i do that??
i get the name of function from url in my index() function but don't know how to call it ??

Thanks in advance.