Question

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? and then respectively use either the strtolower or mb_strtolower if available.

Answer 1

Regex is not able to change characters by itself, it can only change their order and/or add additional characters/delete some of them.

There is preg_replace_callback or /e flag, but they can manipulate only with known functions, and therefore can’t do better than strtolower.

If you can’t rely on existense of mb_strolower function, you will have to implement it yourself.