PHP 生成唯一會話ID ，帶橫線 字符串

<?php

 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;
       }
echo create_guid();
?>

2E7671F3-4F0E-7B1E-4C6E-144789B8BC67