How to remove diacritics from text?

Question

I am making a swedish website, and swedish letters are å, ä, and ö.

I need to make a string entered by a user to become url-safe with PHP.

Basically, need to

Answer 1

as simple as

 $str = str_replace(array('å', 'ä', 'ö'), array('a', 'a', 'o'), $str); 
 $str = preg_replace('/[^a-z0-9]+/', '_', strtolower($str));

assuming you use the same encoding for your data and your code.