Specify the encoding in HTML and use mb_strtolower() to convert case:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 TRANSITIONAL//EN"> <html> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8"> <head> <title></title> </head> <body> <? $string = '' ; echo mb_strtolower($string, 'UTF-8'); ?> </body> </html>
In the meta tag, it looks like this:
Without a meta tag, it looks like
цукенгшщзхъфывапролджÑÑчÑмитьбю
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