I just stuck at this and cannot find solution. 
I would like to try to transform a string to lower case using `preg_replace`.
I just cannot create the right regex.
The reason is that normal `strtolower` does not support unicode characters.
I know that I could use `mb_strtolower` but this function seems to be quite slow and beside them not everyone has MB support.

Any clue?

Regards,
Radek

EDIT: Ok, thanks alot for your help guys. I think my approach was not quite correct.
I think it would be much better to use this: [How do I detect non-ASCII characters in a string?](https://stackoverflow.com/questions/6497685/how-do-i-detect-non-ascii-characters-in-a-string) and then respectively use either the strtolower or mb\_strtolower if available.