PHP生成唯一用户标识GUID

//生成唯一用户标识id

function create_guid() {

    $charid = strtoupper(md5(uniqid(mt_rand(), true)));

    $hyphen = chr(45);// "-"

    $uuid = chr(123)// "{"

        .substr($charid, 0, 8).$hyphen

        .substr($charid, 8, 4).$hyphen

        .substr($charid,12, 4).$hyphen

        .substr($charid,16, 4).$hyphen

        .substr($charid,20,12)

        .chr(125);// "}"

    return $uuid;

}