PHP

normalizer_normalize($string, Normalizer::FORM_KD);

normalizer_normalize -- PHP Normalizer class

JS

String.prototype.normalize()

str.normalize('NFC');

String.prototype.normalize()

Implementation

static function normalize($string, $form = Normalizer::FORM_C)
{
	return normalizer_normalize($string, $form);
}	

$tag = Ut::normalize($tag);

Transcoding

\UConverter::transcode($sString, 'UTF-8', 'UTF-8'); // strip bad bytes against attacks