Function to prevent special characters in nickname

开发者_开发知识库I've a website where users can register. I would like to prevent all special characters, accents, etc in the nickname (used to login).

I use PHP. How can I do that ?

Edit: Another question, can you give me a regular expression (in PHP) who allow ONLY the 26 letters : abcdefghijklmnopqrstuvwxyz and no more ?

Thanks

$username = preg_replace('/[^a-z]/i', '', $username);

If you really just mean lowercase a-z, remove the i flag.

In response to comment, the regexp becomes [^a-z0-9]

You could use PHP's normalizer functions for that.