[ASK] How to change capitalize to lowercase and replace spacing with underscores

[eluser]senz[/eluser]
Hi all,
I wanna ask something, how to change capitalize to lowercase and how to replace spacing with underscore?... Because i wanna change the title of my article into database and convert them. Ex : My New Article -> change to -> my_new_article.

Is there any function in codeigniter and how to implement into controller?