How to detect UTF-8 string in PHP

detect-utf8.php

<?php

function isUtf8($string)
{
    return preg_match('%(?:'
      . '[\xC2-\xDF][\x80-\xBF]'                // non-overlong 2-byte
      . '|\xE0[\xA0-\xBF][\x80-\xBF]'           // excluding overlongs
      . '|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}'    // straight 3-byte
      . '|\xED[\x80-\x9F][\x80-\xBF]'           // excluding surrogates
      . '|\xF0[\x90-\xBF][\x80-\xBF]{2}'        // planes 1-3
      . '|[\xF1-\xF3][\x80-\xBF]{3}'            // planes 4-15
      . '|\xF4[\x80-\x8F][\x80-\xBF]{2}'        // plane 16
      . ')+%xs', $string);
}

It works perfectly, thanks!

Not always prefectly. Try isUtf8('SPÓŁDZIELNIA')