This function support utf-8 encoding, Human Language and Character Encoding Support:
<?php
function mb_strrev($str){
$r = '';
for ($i = mb_strlen($str); $i>=0; $i--) {
$r .= mb_substr($str, $i, 1);
}
return $r;
}
echo mb_strrev("☆❤world"); // echo "dlrow❤☆"
?>