I am new in Ci can i use "-" in function as i need clean url

for example

my URL is below:
 www.xyz.com//test/media\_page?media\_id=1&course\_id=2

but i need below: 

www.xyz.com/test/media-page?media-id=1&course-id=2

when i change the function is saying some errors so i am confirming this so if anyone having the idea please share with me.

thanks in advance....

please tell me more things if for this i have to change any more things.