- preg_replace: documentation ( source)
<?php
$result = "°Freen\x18 ew°\x90ɮ\x7F";
$result = preg_replace('~[\x{0000}-\x{001F}\x{007F}-\x{00a0}]~', '', $result);
/*
//reject overly long 2 byte sequences, as well as characters above U+10000 and replace with ?
$result= preg_replace(
'/[\xC2-\xDF]((?![\x80-\xBF])|[\x80-\xBF]{2,})/S',
'', $result );
*/
echo $result;