V
preg_match_all('/./us', $text, $ar);
$text = join('',array_reverse($ar[0]));
// if there are numbers in the string so the next line reverse the number back treat also numbers with dot (decimal) and email
$text = preg_replace_callback('/\d+-\d+|\d+|\d+\.\d+|\S+@\S+/', function (array $m) { return strrev($m[0]); }, $text);
}

