private function buildRequestMysign($para_sort)
{
//把数组所有元素,按照“参数=参数值”的模式用“&”字符拼接成字符串
$prestr = $this->createLinkstring($para_sort);
$mysign = '';
switch (strtoupper(trim($this->sign_type))) {
case 'MD5':
$mysign = $this->md5Sign($prestr, $this->key);
break;
default:
$mysign = '';
}
return $mysign;
}