/**
* GUID生成函数
* @return string
*/
function create_guid() {
$charid = strtoupper(md5(uniqid(mt_rand(), true)));
$hyphen = chr(45);// "-"
$uuid =
substr($charid, 0, 8).$hyphen
.substr($charid, 8, 4).$hyphen
.substr($charid,12, 4).$hyphen
.substr($charid,16, 4).$hyphen
.substr($charid,20,12);
return $uuid;
}