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

Here is my implementation to filter out 4-byte chars

$string = preg_replace_callback(
    '/./u',
    function (array $match) {
        return strlen($match[0]) >= 4 ? null : $match[0];
    },
    $string
);

you could tweak it and replace null (which removes the char) with some substitute string. You can also replace >= 4 with some other byte-length check.