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

// normalize data (remove accent marks) using PHP's *intl* extension
$data = normalizer_normalize($data);

// replace everything NOT in the sets you specified with an underscore
$data = preg_replace("#[^A-Za-z1-9]#","_", $data);