php的MCRYPT_RIJNDAEL_256 和mcrypt_encrypt 用法

<?php
$key = "miyao";//密钥

$string="jiami";//需要加密的字符

$d = new d();

//加密
$crypttext = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $string, MCRYPT_MODE_CBC, md5(md5($key))));
$encrypted =trim($d->safe_b64encode($crypttext));//对特殊字符进行处理

echo $encrypted;

// 解密

$key="miyao";
$crypttexttb=$d->safe_b64decode($encrypted);//对特殊字符解析
$decryptedtb = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($crypttexttb), MCRYPT_MODE_CBC, md5(md5($key))), "\0");//解密函数

echo $decryptedtb;
//处理特殊字符

class d{
    public  function safe_b64encode($string) {
        $data = base64_encode($string);
        $data = str_replace(array('+','/','='),array('-','_',''),$data);
        return $data;
    }

//解析特殊字符

    public function safe_b64decode($string) {
        $data = str_replace(array('-','_'),array('+','/'),$string);
        $mod4 = strlen($data) % ;
        if ($mod4) {
            $data .= substr('====', $mod4);
        }
        return base64_decode($data);
    }
    public function s(){
        echo ;
    }
}

?>