How to replace/remove 4(+)-byte characters from a UTF-8 string in PHP?

Question

It seems like MySQL does not support characters with more than 3 bytes in its default UTF-8 charset.

So, in PHP, how can I get rid of all 4(-and-more)-byte character

Answer 1

Another filter implementation, more complex.

It try transliterate to ASCII characters, otherwise iserts unicode replacement character to avoid XSS, eg.:

$tr = preg_replace_callback('/([\x{10000}-\x{10FFFF}])/u', function($m){
    $c = iconv('ISO-8859-2', 'UTF-8',iconv('utf-8','ISO-8859-2//TRANSLIT//IGNORE', $m[1]));
    if($c == '')
        return '�';
    return $c;

}, $s);