<?php
class CryptoStr{
    //中间加密字符串
    function getCryptoStr($str) {
        $len = strlen($str);
        $first = substr( $str, 0, 1 );
        $last  = substr( $str, $len-1,1 );
        echo $first."****".$last;
    }

    function getCryptoMbStr($str) {
        $len = mb_strlen($str,'utf-8');
        $first = mb_substr($str,0,1,'utf-8');
        $last = mb_substr($str,$len-1,1,'utf-8');            
        echo $first."****".$last;
    }
}
$obj = new CryptoStr();
// $obj->getCryptoStr('zabcs6');
// $obj->getCryptoStr('中国');

$obj->getCryptoMbStr('zabcs6');
$obj->getCryptoMbStr('中国');
?>