Remove any non-UTF8 characters

gistfile1.txt

//reject overly long 2 byte sequences, as well as characters above U+10000 and replace with ?
$some_string = preg_replace('/[\x00-\x08\x10\x0B\x0C\x0E-\x19\x7F]'.
 '|[\x00-\x7F][\x80-\xBF]+'.
 '|([\xC0\xC1]|[\xF0-\xFF])[\x80-\xBF]*'.
 '|[\xC2-\xDF]((?![\x80-\xBF])|[\x80-\xBF]{2,})'.
 '|[\xE0-\xEF](([\x80-\xBF](?![\x80-\xBF]))|(?![\x80-\xBF]{2})|[\x80-\xBF]{3,})/S',
 '?', $some_string );
 
//reject overly long 3 byte sequences and UTF-16 surrogates and replace with ?
$some_string = preg_replace('/\xE0[\x80-\x9F][\x80-\xBF]'.
 '|\xED[\xA0-\xBF][\x80-\xBF]/S','?', $some_string );