php基于mcrypt_encrypt和mcrypt_decrypt实现字符串加密解

$key = "miyao";//密钥
$string="jiami"//需要加密的字符
//自带的加密函数
$crypttext = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $string, MCRYPT_MODE_CBC, md5(md5($key))));
$encrypted =trim($this->safe_b64encode($crypttext));//对特殊字符进行处理
$key="miyao"
$crypttexttb=safe_b64decode($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
//处理特殊字符
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) % 4;
    if ($mod4) {
      $data .= substr('====', $mod4);
    }
    return base64_decode($data);
}